Honestly the whole system could be fixed by getting rid of re-entry bars and/or re-instituting 245(i). Prior to IIRAIRA in 1997 people would come illegally or overstay, eventually marry or find an employer to sponsor them, and then either do consular processing or pay the penalty, or they'd just leave fully knowing that the doors aren't shut behind them.

Undocumented population ballooned after those safety valves were removed. I heard a lot of people who are unhappy in US but won't leave because it's a one way trip.