...I don't think Plague Knight's supposed to be able to spam bomb-throws to save himself from bottomless pits.
Like, actually, I just went to Arid Canyon act 1, went to the final checkpoint, and just jumped off. It was an absurdly long fall, yet all I had to do to rise ALL the way back UP was... just, toss more bombs. At some point I had to time my bomb tosses a little bit, but otherwise... Yeah. I don't think that's supposed to be a strength of his.
...Not without Arcana, anyway. I imagine the Vat or the Staff of Surging would very much help you recover from pits and the like. And one of those is actually here! Yeah, I didn't realize it at first, but the Staff of Surging is a battle ability! And it very much does indeed help with pits, in a more fun way than the strange bomb-toss-into-bottomless-pit-to-fly thing.
I don't think you're supposed to be able to bomb-burst in the middle of a Staff of Surging uppercut, though? Or throw bombs? Throwing bombs in particular seems to stall the Staff of Surging, either making the startup much longer, or sending you absurd heights. I think the way Plague of Shadows handled it was just preventing the bomb-burst and canceling the charge, and also not letting you toss a bomb before the Staff attack finishes.
Hitting a horizontal spring in the middle of the uppercut retains all your upward momentum. Not a common scenario, requiring a horizontal spring somewhat above the ground, but when it pops up, you can launch yourself absurdly high in the air.
Also, any rings collected after you use the Staff of Surging when you don't have 10 rings disappear when you land. Very odd. You could use the staff at 0 rings, aim at a pair of ring-boxes, and get 20 rings from that, and when you land it just vanishes.
As for the general playstyle... I love it! He plays in many ways like how he actually does in PoS! The ways momentum works tend to change around some strengths of his, though. For an example, with SRB2's air physics (as of V2.2.9), trying to move from a standstill in the air is super slow, making a bomb-burst straight up feel sluggish, whereas in PoS I remember using neutral bomb-jumps all the time after using a directional one to control myself without dropping like a brick. Aside from that, however, Plague Knight is exactly like how I imagined him playing like after noticing he was put in SRB2, with all the strengths and weaknesses I expected.
Finally, the auto-aim is neat, but as I usually find with non-hitscan autoaim (like MM8BDM weapons) it can be as helpful as it could be obstructive. Sure, for bosses like the Egg-Arena in CEZ3 I don't see any reason not to use it, but when I'm trying to snipe Metal Sonic and it makes me aim where he is and not where he's going to be, I tend to miss a ton. I think I'd like the option to turn it off.
Overall, I feel this is an absurdly fun character to blast through the game with! Bomb-bursting through Arid Canyon, blowing up Eggman from above, or using the Staff of Surging in singleplayer maps for that extra bit of height was... a truly bombastic experience.
Now I just need to play some actual Battlemod matches with him.