Pretty specific question about how to do something with multisite and wpmudev plugins

Hey everyone, I just signed up for wpmudev and I have a pretty specific question about how to do a specific thing for my multisite website using the wpmudev plugins.

Here goes. Ok, I want to make it so when users make an account, they automatically get a site without it asking them. But I also want the site to be really restricted in what they can do. Meaning I want it to have a default look and theme that they can't change. And I want them to not be able to access all the features of wp-admin. All I want them to be able to do is make blog posts, and upload digital products to put in a marketpress store.

Is all this even possible? And if so, how can I do it?