I think that still has the issue on the Additional Privs page (if kept as a checkbox) that if a community designates, say, 20 different Roles, that'll be a very wide matrix. There's the option of putting an arbitrary cap on the number of Roles that can be defined, but honestly I kiiiind of feel like if community administrators want eleventy billion different Roles then to some extent they can deal with that not being presented super gracefully when it comes to assigning them?