My theme for year 2018 - AppStrap Bootstrap 4 by themelize.me
Now only limit is e107 itself. This is bootstrap 4 theme, so there will be some workaround , but the lack of new plugins can be limited too.
I don't know if I do paid themes or if I change this site to some membership club. But I know that I will focus on this template and plugins to be able to fully using its possibilities.