Is it possible to associate a blog template with a pro-site

Hi
Is it possible to associate a blog template with a pro-site level and make it the default template for that level.
Am asking this because I building a network where the community will be on the main site and market will be on a subsite. and at the same time I wan't members to be able to choose to either create a site or a store. and since to create a site it will have to be done from the main site since we can't have subsite of a subsite. I thought about creating different levels of pro-site levels where if a member chooses to create a store there will be one blog-template created to have the same look all over the market place and like that I can have an etsy like site. and if a member wants to create a site they choose a different level of pro-site level where many themes and plugins will be available and the blog template won't be a default.

so to summarise I want a default blog template for when a member wants to create a store or chooses the pro-site level for this feature. and many blog templates to choose from when a member wants to create a site.

I hope I made since as it got me in a dilemma

thanks a lot in advance