How to allow payment for one plugin

From what I can tell, this should be doable with either Upgrades, Supporter, or some combination...I'm just not sure the cleanest way to go about it.

I'm using Supporter and enable "supporter" themes and plugins, and remove ads, on paid blogs. Additionally, I've checked the box to allow users to "Disable Ads" and to also allow premium themes on those additional blogs.

BUT, there is no function to also enable premium plugins on those additional sites.

Specifically, domain mapping is one of my "supporter" plugins. I wanted to give Supporters the ability to use domain mapping on their additional, "Disable Ads" blogs.

It seems like there are 2 ways to do this:

1. Hack supporter to allow "supporter" plugins on Ad-Disabled blogs.

2. Configure the Upgrades Plugin to specifically allow the purchase of domain mapping for one or more sites.

Option 2 would be my preference...and it would be REALLY slick to to have a "Use a Custom Domain" link in a member's dashboard where they could enable domain mapping for a small fee.

Obviously, this applies to any plugin and the concept of making them available to members a-la-cart. In trying to research the Upgrades plugin, this seems possible, but would take a lot of back-end work as the plugin isn't too user-friendly.

Any guidance would be much appreciated!