Supporter functionality on a shop basis...

Hi guys!

I love the supporter plugin but it has limited functionality for me.
I would like to:
a) Be able to sell certain plugins (on an Appstore - like basis) and let them be automaticly turned on when the payment checks out
b) Be able to sell certain themes (on an Appstore - like basis)

My customers don't know Wordpress and they are not looking to buy certain functionality - I would like them to buy plugins and themes and pay for each one.

Has anyone done anything like this before and how?