Request more Support ctustomization

Here is what I am wanting to do. I want to be able to charge for things separately. I am mostly interested in selling my users space and allow them to buy chunks at a time. For example, I want them to be able to purchase 1GB of space at a time. I also maybe would like to allow them to purchase premium plugins for maybe 99 cents per theme or whatever I decide the price to be.

Is there any way to accomplish this with the current theme? I only seem to be able to provide a single space upgrade to the users.