While I agree that a PVP/Survival/Raid server IMO would be better, I think in the end it's upto the regulars to have the final say.
I can't see how you could raid a locked chest, and on it's own I think your suggestion would be even harder to regulate Noes. If somebody wants to get into a building and kill/steal your stuff they WILL break walls, that's inevitable.
Xeno's going to kill me for suggesting this.
Bear with me Xeno.. but how about Factions? To me it seems to be a very suitable option. It will protect your area from greifing provided your faction power ( Gained over time by not dying, lost by dying. Usually tops out at 10/10 for each player, it adds up in the faction and that dictates how much protected land you can have ) does not drop below the total land acquired by your faction. The Chests inside are also protected and not openable and offers a very similar experience to what is provided at the moment ( you claim your chunk and it is protected! ). However It will implement another aspect to the game, PVP unwanted visitors, Raid others for extra resources, Faction battles, etc.
Sorry if that's a bit long winded.
