I love arena, so I'd love to see this on arena.
Tips for arena as far as I would go is to give the player a lot of path options(lumberyard does this, so do a lot of valve arena maps), the player only has one life, so they won't want to waste it. Also, a good arena map should be as balanced (to any class) as humanly possible, seeing as it sucks to have dominating classes (i.e. scout and sniper can be very popular in watchtower)
You should only have 1 health pack, and try to get a good amount of ammo, but not so much so that everyone is running full all the time, keep in mind ammo=engies.
Good sentry spots can be a no-no because IMO nothing is worse than a sentry stopping you from killing some retard player.
Hope that helped as far as arena goes!