I just thought of what I think would be an awesome thing to do.
Let players change fire modes with the button they use to clear ghost bricks, with all weapons having a mode for "safety" (to avoid misfires), and automatics having modes for single, burst, and auto as well. Fire mode would be displayed next to ammo. Gravity Cat's DWeapons grenade launcher and some Blockcombat automatics (HK416, Famas, etc.) use fire modes.