aim time would never be an upgrade in any multiplayer mode.
also, i was thinking of tipped arrows, such as:
sticky bomb arrow: this arrow sticks to players, and has half the explosion radius of a spider-tron exploding.
electric arrows: arrows that don't chip anything off the enemy, but electrocute the enemy 3 seconds after impact, ending his life.
scatter arrow: an arrow that scatters into multiple smaller arrows upon hit anything (including enemies). you can only choose one arrow, and it costs 1 energy to tip them (the keybind is F), but if it is combined with your idea for quivers, then you can store them beforehand to use during battle.