Player groups for ULX, and server, in generale

Yallo peeps, so let me get to the point; basically, first of all i hope im posting in the right forum
here is me problem:
my server has a good population, and its basically kinda mix, somewhere where people can have random death matches, or can build to their heart’s content.
this is what i want to do: i have created player groups, such as a builders group, where those who only want to build can join, and they are given god mode, so that they dont die when other random people come and fight; so yeah, that group is working fine, but there is a teeny problem. you see, i want it so that people can automatically join that group, for eg. by a command:!group builder instead of asking an admin to put them in the group, and or remove them, since i dont have admins online all the time, so people are left stuck in a group. I just wanted to know is there a way where the people can join the group themselves, like with a command, and when they want to exit, just type in the command again, and get outta the group?
Dankes so much for yer helpe peepils =)