Pro Sites Extra Options

Hi,

I am wondering if marketpress can integrate with pro sites.
I would like to offer add-ons to customers, which they can add on to any existing website plan, essentially modifying it.

For example they can have extra design features upon sign-up (pay $400 to have a designer create custom graphics for you) or pay an extra 2.99/mo for priority support...

Can this be done right now, or can this be requested as a feature? To me it would make perfect sense, but I haven't seen the idea anywhere...

Thank you in advance