Giving Users Access To Multiple Paid 'Memberships' (Groups or Products) At The Same Time?

What is the simplest way to grant paid access to multiple paid “Memberships/Groups/Blogs’ etc at the same time?

I’m building a site in which I want to sell training courses… basically membership sites.. and I need to find the simplest and most flexible way to manage the payment and access to these in one site. Our ‘Info Products / Memberships’ would be purchased in something that resembles a store front, but a user could choose which memberships to buy and have access to only those.

These memberships may consist of just one page or download (an eBook or report for example) OR they may be multiple pages exactly like a free standing membership site with lots of embedded video and possibly dripped content.

For example:

User 1 buys memberships 1,3 and 5

User 2 buys memberships 1,3,4 and 7

Each user has access only to the memberships that they purchased and can see all of their purchases from their dashboard.

I’d like to host all of this on the same site if possible but I need a fairly rich feature set. I’ve looked at DAP (Digital Access Pass) since the drip feature there is excellent but I think that may be overkill if there’s an easier way just using WPMU plugins.

Help appreciated.