You are already around 4 minute on the roof immune against melee and cav. You dont need to be on roof to last second, best archers are rarely on roof at all.
Kick people for admins will be easy, they can take screenshot, give little warning and then kick, so nobobady can complains.
it would require an admin to kick them instantly and second,
Now admins for some weird reason not kick people when they are last instantly, not much change.
Only problem i can see is when only one team have admin, he obviously kick enemy archers first, but if i will be in team without admin, i like sacrifice my multi for better enjoyable game.
EDIT: also for players will be very easy take screenshots of roofcampers, and if somebody frequently breaking rules, write a ban demand. I'm sure many players would love to see this players be banned for some time. So admins on server probably can play almost normally and players take care about rooflovers.