So my suggestion is that an option is implemented that will make it so that units cannot be in 2 control groups at the same time. So that if you have, let´s say, 10 roaches in a control group and wanna send 3 roaches off all you have to do is box 3 roaches and make a new control group to remove them from the first group.
(I didn't know what to put in the title but this was the best I could come up with.)