There needs to be a system of doing long actions "in combat". Basically, what should happen is that if you have less AP then an action takes, you get less AP next turn (including, possibly, no AP if it's something that takes over 4 seconds). This would also allow you to do complex actions (like picking a lock) under fire. The only problem is that the action should, by right, be resolved after you get that AP, which could be somewhat problematic if we're talking about shooting someone, and downright bug-like if you want to hit them in melee. Perhaps you get to chose if you want to continue doing the action during of the next turn?