I was thinking of making a feature request about this. I would love to integrate more AppThemes themes into my website. I already have the classipress going nice, getting around ten new ads daily. It would be cool to also have the Vantage, Clipper, and Sage themes integrated into new sections of my website, then my site will be a behemoth for it's niche, with classifieds, directory/reviews, coupons, and how to articles.
One thing to consider is we wouldn't want a separate profile for all the different themes. I don't want members of my site to have multiple profiles all on one website... actually this is already the case because my site has profiles associated with classipress and also profiles associated with a bbpress forum.