Site creation flow with Pro Sites

I’m trying to achieve certain flow on registration/site creation process and maybe you can help me get the backend/plugin settings correct to get desired effect.

Since we use Pro Sites we created levels as we want to able to control and upsell premium plugins/functionality and themes using Pretty Plugins, Themes Manager and New Blog templates.

So since we have levels the signup form displays tables/levels.

User has to select level before setting up sub site.

Default account confirmation is in place and we have set blogs and accounts can be registered in settings and Free level disabled.

Is there a combination of settings (or a plugin) to have a flow of signing up similar to EduBlogs (going through steps)?

Can we register users, they create a site on Basic level, then they can upgrade?

How does having users register first before creating a sub site affect process?

Do you have a cheat sheet of different combinations of site settings and plugins to achieve different setups?

Thank you.