Membership: Can I charge someone ONCE and at the same time assign him a custom role?

Is it possible

a) To set up a subscription that is a "once off payment" as in non recurring? I have MarketPress installed and was going to use Mpress to sell a "premium membership" which is a once off purchase...

b) the problem is i want that premium member to have "special access rights" and this is where i set up a "premium member" ACL in membership premium. In my case i want ONLY these premium members to be able to set up a blog on the site, and ONLY they can invite people to THEIR blog (using Secure Invite)

I also have Pro Sites installed, trying to see how to do this best.

Apart from this these premium members can still upgrade to other sub packages e.g. Bronze Silver etc which is a monthly sub controlling content level access

In a nutshell the Premium member is a special role guy, who can set up own blog and groups, and invite people to his blog, thats really all