Here is an idea to make aiming and shooting more challenging in a 2D Soldat-like game. Basically the bullets travel in a 2.25D plane instead of just crossing the screen. The bullet fires at the point your mouse cursor is actually at. So to shoot a dude in the head you must aim just like in an FPS – at his head. These pictures explain it all.
The last picture shows why this approach is correct from a realism point of view. It is still to be considered if it is fun and has gameplay value. I’ll definitely try it out in Link-Dead.