Not being a Trib player I don't really know how the intercity teleport works or if there are limitations to its use, but in general it just seems too convenient for Tribs (not only in this case if Arkham were made a Trib city). I say have Tribs walk between cities like everyone else and thus more possibility for action.

As for the suggestion otherwise, I think the main issue is having Scarab in Arkham, which could be solved by moving them say to the old Scion location.