Looking for a way to let players choose a role/spawn region via Command Blocks (or a mod)

[RickForge]

I'm working on a server spawn/hub and would like to let new players choose a starting region when they join.

Idea: 

Players arrive at a spawn hub to read rules etc. > They click a command block for North, South, etc. > The player is assigned a role (e.g. suplayer_north). > Get teleported to the role's spawnpoint.

The problem is setting a role and I've been experimenting with Command blocks and the closest command I've gotten to work is:

"/executeas admin-name /player o[range=5] role suplayer_north"

This works, but only when the specified admin is online and within range. 

With "/player s[] role suplayer_north" I get "You can't change your own group"

 

Now I'm kind of lost and I'm not sure if this is a limit of the vanilla game at this point or if I'm missing something important. I also can't seem to find a caller replacement for an admin name that would be console/server.

Any ideas, suggestions? Mods? Any help would be appreciated! 

 

 

 

 

Edited May 30 by RickForge