I guess I could share this here.
So I think people that have been around FFX's GameFaqs have heard from the Pbirdman Mod, it is a massive project that Pbirdman on it for a very long time (over 8 years), and recently a Youtuber name Dansg08 was doing a beta test run of it that took 2 years to complete and after all this time the mod is available publicaly, I let Dansg08 do the presentation of the mod has he made a great video for it :
So overall what to expect ?
The mod is advertise as not an Hardcore hack but rather a progressive difficulty, that start relativly close to the original and progressivly gets harder.
Furthermore if you familliar with a LandonRay's Punishment this is a completly different philosophy, Punishment was mostly increasing the stats of ennemies and nerfing the Sphere Grid, this mod goes further of course it tweaks some ennemies stats but it mostly changes the AI of the ennemies, add new attack to them or new effect on their existing attack. It also tweaks some game mechanics to balance things out, to my acknowledge the most ambitious gameplay mod for FFX so far.
As a disclaimer I watched Dansg08 story part of his run but this was 2 years ago now so I forgot mostly everything regarding to the change done to the ennemies (and some things have been tweak by PBirdman base on feedback from that playthrough) so for Story part this is mostly a discovery for me, for the Arena Monster to as I didn't watch that part of the playthrough I however did watch the Dark Aeons and Penance fights, tough by the time I reached them I'll probably forget about the changes.
Also other things to note :
-LP is in French cause this is my native language, game is in English and I add description about important stuff to note here.
-The Mod is for the PAL English version, officially this version was the first to introduce Dark Aeons and Penance (among other minor changes), one negative aspect is like most PAL game at the time it was on 50Hz instead of 60Hz and was running about 10-20% slower than the NTSC version, fortunatly from Episode 3 onward I found a program to make the ISO in NTSC and run it at 60Hz, of course can't guaranteed everything in the mod will work as intended but so far the mod runs perfectly fine and I didn't encounter any issues (and the save are compatible with both ISO so if I encounter an issue I can just go back to the 50Hz one), except some synch problem with animation and sound during cutscenes and some attacks but these doesn't affect the gameplay.
-The mod can only be played with the standard sphere grid rename Challenge Sphere Grid, which I think in a mod is good as the Standard Sphere Grid keeps each characters in their own roles which makes thing easier to balance around (for the main story anyway)
-PBirdman guaranteed that he didn't make this mod as a grind fest (except for post-game superbosses of course this can't be avoided), so for the most I will avoid any unecessary grind regarding stats and will try to avoid getting overlevel.
Alright let's get started first off the 2 first episodes :
Episode 1 : https://youtu.be/nRzalO4zah8?list=PLu3lFfLxm77aA0LXrh57p7QCgXQ2um4FY
Episode 2 : https://youtu.be/f2zNnPkmcWw?list=PLu3lFfLxm77aA0LXrh57p7QCgXQ2um4F
Ok so episode 1 and 2 you can mostly skip them the beginning of the games has pretty much no changes in term of how the ennemies behave and play almost exactly like the base game but we can already see some changes :
-First off and this is a big one the Overdrive Gauge takes Double time to fill, what this means is we will not get nearly as much Overdrive as we can in the base games, this is a game changer as Overdrive are generally very powerfull especially for the main story (and also mean Tidus will take longer to learn his Overdrive unless of course you grind for it).
-Some abilities that were free of charge now cost MP, Cheer cost 1 MP (and according to the Patch Notes is now affected by Silence), and Steal cost 3MP.
-Some other minor Tweak like Wakka's statut effect attacks now last 2 turns instead of 3.
-The Aeon and this is big change has been dramatically nerfed, first off summoning cost 10MP (can't be display in the menu due to technical limitation) and is afflicted by Silence, furthermore the Aeons are no longer immune to statut effects, their special abilities cost MP and the biggest change their Overdrive charged 4 TIMES slower than in the base........ YEAH don't expect to cheese the boss fight with Aeons here, on a side note since charging Aeon's Overdrive is so long this makes Yuna's own overdrive more usefull.
Also some sphere grids change :
-Every MP + 20 has been turns into MP + 10 cases so we'll get less MP in general (there is also another major changes about MP but it's not relevant yet)
-Every abilities that allow to turn ennemies item drop into sphere has been remove (IIRC this was introduce in the PAL/INT version so if you are accustome to the base NA version this isn't a big change)
-Some abilities have been moved most noticeably so far Flee is behind a LV2 Lock now and so won't be available for now.
-A change that affect Kimahri the character paths are locked behind LV3 Lock except Tidus and Lulu's one which are lock behind LV2, not sure how I feel about this change honnestly.
For battle the only fight worth talking about in the first 2 episodes is the one on one Kimahri fight on Besaid, Kimahri is a little more dangerous as he uses Seed Canon and Aquabreath (and also Fire Breath if you let him time to do so), it makes the fight a little more serious but not anything crazy.
Episode 3 : https://youtu.be/xUlBIv2GPNw?list=PLu3lFfLxm77aA0LXrh57p7QCgXQ2um4FY
Now Episode 3 is where we see some big changes on the ennemies :
-Besaid Mob fight have been overhauled they have more HP so Overkilling them isn't possible, the Condor resist all element and can cast Water, the Water Flan has Auto-Shell can counter magic.
-Sin Fin fight : This was the wake up call fight as far I'm concern, the Vanilla fight is a complete breeze and also a good farming spot as you can kill the little ones again and again for massive AP gains and items, well not worth doing here as the little adds gave No AP and only 25% drop.
As for the change the Sin Scales have a little more HP and can now heal themselves with Potion, but the biggest change is they hit like Fucking Truck for this point of the game and takes no time to charge their Spines, the best way is without a doubt to kill one ASAP as if the 3 cast Spines back to back this can be devastating (without Cheer only Wakka and Kimahri can survive 2 Spines), the other big change is Sin Fin now whenever he moves he does damage to the entire party but also has 5% chance to Confuse, I get really unlucky at one point and got 2 character confuse at the same time (1 chance out of 400 talk about bad luck -_-).
So Yeah probably the first fight where you'll notice a good difficulty increase compare to Vanilla. Also you'll notice a change EVERY boss is now immune to Scan and Sensor, however the Description with Sensor will give some hint about the changes.
-Sinspawn Ech : I think Pbirdman did go easy on this one which is probably for the best as we just finish a fight, and for this one we only have 2 characters and our only heal is through Potions, Sinspawn Ech is still a little tougher as he has slighy increase Strength and Magic and a 70% resistance to Dark (so 22.5% chance to inflict it with Wakka Dark Attack), still with 5 Cheer their damage are perfectly manageable and Wakka and Tidus hits hard enough to kill him quickly, and I manage to land an Overkill on him with Tidus's Spiral Cut ^^.
After that just more cutscenes
Episode 4 : https://youtu.be/IY6885kUs2I
Now for the Kilika Forest :
-The mobs get tougher here, in fact I have a perfect exemple where I got Ambush against 3 ennemies and get wiped out without getting a single turn geez, the most annoying one is definitly the Thunder Elemental his Thunder is now AoE and can 2 shot anyone except Wakka and Kimahri don't even think beating this bastard without having Yuna with Nullshock, the Lizard is also an annoying one as he has 20% chance to Petrify, the Bees have 80% chance to Poison but for these 2 we conviniently get a Ball for Wakka with Icestrike that makes him able to one shot them (and get the Overkill) with just 1 Cheer, if you want to farm some SLV these 2 are your best shot, as for the Flower as far as I saw she only has more HP.
-I've try the Ochu which in the base game is really easy, and makes one of Luzzu's dialogue about needing 100 crusaders to take him down quite hilarious...... wel let's just say that funny dialog was taken 100% seriously and so this time we're gonna listen to their advice and avoid Ochu for now ^^", so on to the next boss.
-Sinspawn Geniaux is tougher than the base games and have some interesting mechanic, first off he has 4000HP now and goes out of his shell after only 400 damage, he doesn't have a new attacks but Water is now AoE so Nulltide is a good idea here.... except his Water Spell has the effect of making your character RESISTANT to Nulltide basically after the first Water Nulltide will have only 50% chance to work on your character, an interesting change that spice things up, Venom is unchanged and his last attack Staccato has an higher chance to Crit (also his Luck has been increase from 1 to 17) and also 20% chance to inflict Sleep for 1 turn.
And that's all for now, so far the mod looks really promising, I already know that the changes are only gonna get more and more complex from now on, for now I highly recommend giving this mod a run if you want a new FFX experience.