I think having the ability to have smaller cap ships ram larger ones and large ships ram space stations would be cool. The ram command should re-direct power from the ship's shields to it's engines making it faster, but easier to destroy. If shield generators have been destroyed, then the ships should move at normal speed.
Also, a self destruct mechanism for capital ships that does large ammounts of splash damage would be cool as well. There needs to be something you can do to your heavily damaged ships so you can replace them with new ones!