The end game involves restoration of the monarchy, a sanhedrin and an kohen gadol. It’s the middle game that’s problematic. In such a state, all military units would resemble hesder units, and hilonim would be in charge of nothing more important than cleaning latrines.
In the interim, and realizing that it is probably impossible for a zionist state to ever make peace with the goyim (a major factor in our gedolim having opposed the zionists), they should switch to a professional army. Based on the percentage of volunteers for combat units, they shouldn’t have a problem. If they want frum recruits, they’ll have to offer them terms and conditions of service that are attractive.