I like the idea of getting rewarded for surviving, but I think it should be based on how many waves we survive, an enemy better deployment system, increasing enemy difficulty and a goal. For surviving say at the end of 3 to 5 waves we get the choice of reinforcements, a power weapon or a vehicle so we can survive longer. The deployment system from reach was to scripted we knew where they were going to land I think the landing parties should be randomly generated and the maps main building be attackable from all directions. The increasing difficulty is where as the enemies don’t get stronger but they get smarter. Lastly With the goal maybe 3 modes Classic, Timed and Waved, so the classic is like the normal firefight but the other 2 require you to hold out for an amount of time where troops deploy on a time based system to avoid people keeping 1 grunt alive and winning, and the Wave based is where you have to hold out against waves and a boss at the end or regaler intervals