Don't see why not. Nadine Coyle created her own record label in order to release her solo album, so Katy certainly wouldn't be the first musician to do so. It is an awful plan though, unless you're an expert in the industry...
Like, without Capitol we probably would've gotten Peacock as a single. And imagine how rubbish the video budgets would be...
I'm not getting a good feeling about this label thing...
Katy was Capitol's only big popstar, but Universal has others, so I'm thinking she won't get that much promo. It is (or it was?) everything so perfect at EMI (at least for Katy and Coldplay), the music videos, the covers...