Joseph-
The Rambam is clear that sheivet Leivi is exempt from the army and that anyone who wants to “join” sheivet leivi can by learning full time. But, the Rambam is also clear that no one is allowed to take money for learning. So if we’re going to use the Rambam as the basis that anyone learning in kollel is exempt from military service, than we should also discontinue the kollel stipend as per the shitah of the Rambam.