Let Israel institute an all-volunteer army like the United States.
I don’t understand why anyone would want to force people to stop learning Torah all day to go to an army that does not have a need for additional soldiers than they already have. As it is they have enough soldiers. If you take people away from Torah and make them soldiers, the Israeli Army will simply have to reassign others who were never learning in the first place into some task other than fighting, as they aren’t currently short-staffed as it is. It is absurd to take Torah people away from the Torah to make them soldiers, so you can take soldiers away from being soldiers and make them into cooks or something.
Let the Torah people learn all day. There is no comparison between learning Torah all day and learning half a day. The more Torah the better, and the more Torah the more protection. A full day of Limud Torah does more for Klal Yisroel than a half a day of Limud Torah (with the other half soldiering.)