My apologies but I don't really play iEra, so correct me wherever i'm wrong but I enjoyed reading this thread and thought I'd share my input.
So, from what I've read, some players argue that you should only be able to use a particular gun (M4?) in the arena however those that have purchased better weapons such as the BAR have the right to use them.
So why not just create two types of lobbies for the arena? 'Ranked' (PK Arena based on skill) VS 'Friendly' (PK Arena where all guns can be used)
You would be satisfying all the players, and iEra certainly has the playercount to make this possible, so yeah.