Can Pay-To-Blog be Tweaked for 1 Specific Theme?

Hi,

I'm running a real estate site with free blogs and supporter "premium" blogs @ $25 per month.

I want to be able to offer my users a simple photo-blog for single-property websites and charge them seperately...maybe $5 for 3 months.

Is there a way to tweak pay-to-blog to not interfere with everything else I've done and ONLY apply to a specific theme?

Thoughts?