The current layout wasn't due to a coop design... I just naturally coded it to use WASD and Mouse for fire... But I can see why having your hand on the mouse would make you want to use it to start aiming. A few other people have also mentioned the desire to aim with the mouse... I will definitely look into it.
I personally enjoy the aiming and movement being tied to the same control... I guess I'm a sucker for trying to master the conflicting controls. Deciding when to push or let go was a fun part of it for me.
I won't be doing snap aiming or auto aiming.
I'm not sure I understand this point..."and by splitting it to 2 inputs you added aiming onto 3 more buttons." ...Your earlier suggestion is to split the aiming to a separate input, but here you seem to indicate that splitting it up is overwhelming? I'm also not sure what you mean when you say I added aiming onto 3 more buttons. Are you referring to the direction buttons WASD? There really is no other way around that unless I implement the mouse aiming...
The third fire button in the title screen is just a submit button. It is currently mapped to ENTER or START on the controller... Instead of removing that button and limiting it to only the fire button, I would rather add ALL the buttons I can think of. That's because a player would be annoyed if they had to "figure out" which button starts the game. It's a small thing to ad the other buttons. I just haven't gotten around to that yet.
Thanks for all your input though. It's great that you took the time to talk to me about it.