I don't think there'd be any problem with Punk sticking around if he walked out with the title.
It's all about how it's presented, though. If he's forced in some way it's bad. If he sticks around to gloat despite "not being on the payroll" and then tosses a few guys a bone defending in unsanctioned matches or something it might not bad.
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No problem!
This is a cute and pop genocide of love!