My favourite scenario last year was also a VERY simple and very much "keep the action going for everyone" scenario. You design a route through your field (it should be a decently large one). Then you plant pilons along this route every 150ft.
The convoy team starts at the start point of the route and moves along the route and must complete the route in X minutes (20, 45, whatever). A timer ticks away. Every time the convoy reaches a new pilon, that's the convoy's new spawn point. The attackers can spawn from a whole bunch of convenient locations and can go wherever they please...
BUT... the convoy team can ONLY stay along the road, or 5 feet off the road -- no further.
Everybody keeps respawning and the action is non-stop.
We played this at Maxwell field last summer and Maddog kept our entire team at bay for what seemed like forever at the base of a hill.
Now you know