I can already hear him complaining about fucked up inputs for this already.
Speaking of which, I think this would be interesting since we would not only get some new SF2 and 3 salt out of it, but we would get to see him try Street Fighter Alpha 3, a game which he talked about quite a bit during mid to late 1998 (the WhoaMoses usenet posts)
Manhunt (he already played a part of it, but I mean a full playthrough of it)
Quake 3 Arena online (guaranteed to be a saltastic mess)
Wolfenstein 3D (if simply because the mutants in Episode 2 will drive him nuts)
In fact, old school fpses as a whole (Duke 3D, Doom, Hexen etc) but I'd think the one that would take the cake is Blood on the regular difficulty. That game doesn't fuck around and in the first chapter not only do you have to be very careful on not getting hit (because you die incredibly quickly and there isn't that much health) but also on not spending too much ammo because ammo is pretty scarce at that point in the game.
That game would break him and he'd likely ragequit the game before he finishes the first chapter.
Battletoads on NES. He played the first four levels but good lord was it a mess. I mean, even with rewinds he was dying so fucking much it was completely hilarious (think Forza Horizon 3 where he abused the hell out of the rewind function and he still sucked ass)
A full playthrough of that would be pure salt.
Lastly, there's this rather obscure game called Broken Helix. It's an unique game in that every event happens in real time so you always have to be moving, you can't catch a break (or at least not for too long) or you risk making the game unwinnable (early on in the game, you are descending floors while a couple of mercs chase you. At every floor they arrive they blow up some generators which will electrify the floor they are in. Essentially, an invisible time limit)
Even if chat told him what to do, the game is very unforgiving in that you can't afford to waste time at all, there are several bullshit escort missions, numerous stealth segments, as well as very strict platforming over instant death pits. You can save wherever you want, but saves are limited. Worse, if you die, you go back to the last save point. Didn't save? Game over, back to the title screen, a la Resident Evil.
It's also an old PS1 game that has awkward controls which would only add to his frustration with the game.
If the other playthroughs would be saltastic, this one would probably make him close down his Patreon account if a fan suggested it to him as a Patreon paid playthrough. And that is no exaggeration. It's pretty much what Phil hates all rolled up into 1 package but magnified 1000 times.