chess.com should allow illegal moves and allow people to claim illegal moves

I dont think thats a factor.
But again, it flat out makes online chess a worse experience for no reason and I dont see why that would be a good idea.
Maybe as an option for people who want this, though I doubt that would be many people.

That would just get rid of premoves.
Let's say you have a king and a pawn against 5 queens. You then make an illegal move and your opponent premoves a move back which is now illegal. Your can claim an illegal move and win even though you're dead lost.
sounds like it would create more chances to swindle for the losing side then. the winning player can't premove all his moves.

Wouldn't be hard to code, and I don't see how it would be bad for bullet when bullet otb is a complete mess.
do you know even a bit on how hard coding is?
That would just get rid of premoves.
Let's say you have a king and a pawn against 5 queens. You then make an illegal move and your opponent premoves a move back which is now illegal. Your can claim an illegal move and win even though you're dead lost.