think the biggest obstacle in discussing game scenarios/idea's is how well a given scenario plays out is as much a factor of the site (layout, obstacles, environment, size etc), the marshalling staff (their ability to explain and enforce rules), and the playerbase (the number of players, the regular/visitor balance and the willingness of the regulars/visitors to get into the spirit of a new game mode)
for example, a simple fall back game- there's a long but thin (inb4 ooh matron...) strip of forest as the game zone.
attackers start at one end- get hit you fall back X paces then back in, get one man to the end building/flag/zone and it's game over
defenders start wherever they want- get hit you fall back X paces and your back in but you can't advance. once you've been pushed back into the final zone then it's down to 1 life.
not exactly the most complicated ruleset. and when played with people who either knew, or at least listened to, the rules it works pretty well. however the number of times you'd find folks ignoring the whole "don't advance as a defender" bit and it would ruin the game, as it'd just bog down into a pointless stalemate, with the usual suspects of cheating/overshooting etc soon bubbling up as peoples frustration mounts.
likewise, that same (or similar enough) scenario on different sites, where the terrain made the game zone either less clear-cut or the area was wider making defending from flanking infinitely more difficult, it'd end up with one player flanking (possibly out of bounds if the game zone was ill-defined/that player didn't bother listening in the brief) and just walking up to the flag and game over. play it on a site with a tight choke point (ie not wide enough to push against one side of the line to force a breakthrough) and we're back to the aforementioned pointless stalemate.
or as an even better example- every attempt at introducing an airsoft version of trouble in terrorist town immediately results in a free for all death match as nobody bothers understanding the rules or implementing tactics beyond "we don't know who the enemy team is- just shoot everyone"