Make other money sources more viable to deter people? Having a tier 4 vigilante account is the equivalent to having infinite money. I can vigi for 2 hours, and make more money than I can doing runs the entire day. Then I spend the money to fund my rebel account. The only vigilante I EVER encounter that is non-brain dead is the Dirty Bastards alt gang. They play it right, go untagged 24/7 and have a gang backing you up. Kavala is home to the 1-day vigis who break the rules and give it up the next day, and I 100% agree there should be a time lock to where you can't play as one. Other than that, how are vigilantes such a problem? Their weapon is OP, a spar taser is crazy good. However, getting to that alone without the support of many friends is pretty hard.
tl;dr, lock vigilante license to enough hours that you feel like that are capable of knowing all rules at that point.