Adeptas are more fleshed out in ROSIGMA, so try that submod if they're your jam.
I do plan on doing so after a small break. Still, ROSIGMA is more that a content addon pack, it adds a lot of new mechanics I certainly won't like. Would be nice if some of the content could get "mainlined" into the base mod eventually.
A large part of the problem is just balance, really. Adeptas do already have SOME unique techs and units, they are just so bad you never end up using them, which makes the faction feel like crippled SM.