Hey!
Thanks for promoting and explaining cpenv @Ricardo_Musch!
I wanted to add, depending on how many rez packages you have @pw_simon , it might be worth looking into the example hook below to integrate rez with your ShotGrid config. That might be preferable to recreating all of your packages as cpenv modules.
Also check out this related thread for more details on Rez support in SG and some background info on cpenv.