ph0rk
Friendship is Magic, and Magic is Heresy.
Convert low level spells slots into Sorcery Points. Its called Sorcerer' Flexible Casting.
Yes; and if and when your subtle dominate fails, you have a very likely aggressive creature and no currently available points to help rectify it, because you use all of your immediately available points for this little trick.
Anyway - the magic detecters would know who did it and apply a smackdown. (The rules don't say detect magic doesn't work that way), And the dopplegangers would merely laugh. Or better yet, play along until the moment they stab the person giving them "commands" in the face.