Though it would be fairly interesting if this was Aliens versus Aliens, and everyone was a Basilisk with Advanced Dragoon sniping ability; you'd be able to get the flag, then abuse the walls to confuse your enemy's sense of gravity as they try and fail to snipe you... Interesting as in probably severely annoying, perhaps.

Either way, this will only work if you do Aliens versus Aliens or Humans versus Humans, since otherwise it'd be a balancing hell, probably made worse if you factor in the maps and the humans' jetpack ability.