Don’t do anything. They knew what the payment was going to be. If the value drops, just don’t borrow more until it comes up or the balance goes down.
If you were stupid enough to get funny financing, get a couple part time jobs so you can make those payments you signed for. Or file bankruptcy and move out.
Heres another idea, cut in half the money owed by people who actually were smart enough to lock in fix rates, bought houses they could afford, and have made all their payments on time. Once people see only those that actually pay their bills and live within their means get help, more might try doing it.
Housing prices have gone up and down from the time mortgages came into being. Countless times, I have known people who bought a house only to have it's value drop a year or two later. This is NOTHING NEW! Housing prices/values rise and fall all the time. I, myself, saw this when I was shopping for houses years ago, as well as when I sold a house. What all this is about is keeping minorities in houses, with mortgages the socialists in Congress made the banks grant, when they can't afford them and couldn't in the first place.
Towns and cities are up in arms because when house values go down, people can have them reassessed and OMG!! That lessens the tax base!!