User Assigned Prices

This may sound crazy, but I do it on my site now and it works really well. I'd like the donation module to be able to assign a user a role based on the donation amount. Even the most simple -- if they make a donation, they are assigned to a specific role. Alternatively, with the subscription part of the module, the same could be achieved if the user can decide how much they want to pay for a subscription rather than force the admin to set a price.

I get a lot of users who pay me what they can and some that pay a lot more than others...I'm using a hacked up version of ecommerce and simple access to do this now and would really like to simplify things. Thanks.