Absolutely random teamup! Rinzler's going to be pretty happy for the chance to murder some bugs, so he'd jump in to help without even really thinking about it... and yeah, they'd totally dissolve into snark and slapfights after.

BONUS POINTS if half of why they get pissy at each other is because no really they were actually working together really well and they don't like it.

And always up for showdowns. Just for clarity-- are you offering Prometheus for starting off the murderplot, or for regular showdown things once he gets Model W back?