This is the second time I'm posting this so hopefully I'll get at least 1 reply this time.
I'll make it short:
this plugin doesn't work properly, misses out on crucial bugs and doesn't take advantage of modern Sourcemod tools and extensions. The RunTeamLogic extension is unsupported for a long time, too.
I need someone who knows TF2 coding, I can provide every bit of information about the plugin's structure and what bugs to avoid. We can make a working plugin!
Q. Why not just turn off the Arena queue system?
A. If you do that then teams can easily be unbalanced, and there's no way to fix that currently. Also, they won't scramble every X rounds (can be solved with gScramble, but unbalanced play will still occur).
Q. What's wrong with the Full Arena Teams plugin?
A. I get the sense that its coding is all over the place instead of focused and clean. Also, when someone is a spectator the plugin treats them like a normal player and raises the player limit per team, creating unbalanced play. It may also create unbalanced situations randomly because of incorrect and poorly timed player inspections.