Oh, I agree. It seems odd that a heroes "leadership ability" applies even to people who would never assent to his/her leadership. :)
Now the RG taunt thing, that's a different issue. Now you're getting into basic functionality that would be limited to certain teams. I don't think the game will go in that direction - at least not anytime soon. Arena looks like and functions like Cantina - which is more of a "free for all" style - and that's a good thing, imho (keeping in mind this is a holotable - not an actual battle). It allows all kinds of teams and synergies and opportunities to see how various abilities compliment each other.
Just as some fun examples:
Phasma slows all enemies down, while ST Han speeds yours up!
QGJ lead calls in Rey on an assist, so now she is protected by foresight.
GS calls in Yoda, so now he has foresight to pass around to the whole team.
Poe exposes a high-health team - now Sid drops AoE...followed by IG88's AoE- fun!!
IG86 attacks a Jedi with his special - calling in Dooku. Stunned Jedi. Nice.
QGJ calls in Daka with his assist attack on Dooku. Dooku is all set to counter - until Daka stuns him.
Daka+Eeth+Dooku vs. a slow team = 3 stunners all speed 132 or higher.
IG86+QGJ+GS = 3 heroes who keep calling each other for assists.
RG taunting - taking a ton of damage, then healed up by Lumi - or raised by Daka is something went incredibly wrong.
All kinds of fun combos, that wouldn't be possible if abilities were limited based on team makeup.
You could certainly limit leadership abilities based on faction - but not all abilities. That would undercut the variety and variability possible in arena.