That would require alot of reprograming of the entire comintern doctrine and we already have commando units for all of them. A better idea is to introduce legendary/epic skins for specific troops. Like a skin of the soviet mountain divison you said. You could get the epic skin from securing supply drops or buy it from the shop, then you will have it for life. So once you have an active commando unit just equip the desired skin and enjoy the new look!
Each doctrine could have its own unique historical skin for specific troops.
