I have an even simpler idea - restrict the vote to those who have served in the military or civil service for a term of time and left under honorable terms. One hitch in the military or 20 years civil service.
Heinlein had the right idea; the vote should only be given to those who have proved that they are willing to put the good of others above their own interests.
Or give birth to one child that is being supported without state help.