AlterBrains

Will this tool also work with JomSocial-modul-positions? Would members for example be able to change positions in the community?

No, it won't work with JomSocial.
But it's a good idea, we will try.

This would give members a great chance to create "their" community. I could publish more modules and they could arrange the most used ones to the top ... if this would be possible, I'd buy.

In fact users can organize apps in their profile page right in JomSocial.

Yes, but only apps on "their" page, not the modules, published by site-admin - for example on latest-activity page.