If I find a village I want to keep populated, I do the torch thing also (or I put jack-o-lanterns level with the ground). But I don't put up a wall. I up the number of doors in the village by expanding doorways and adding houses so iron golems will spawn naturally. Helps to throw lots of bread at the villagers just after putting in the doors to get their numbers up. After that, everything seems to work fine. Just be sure the lighting is effective a little way out of the village so the golems can keep up with the zombies that wander in.
Worst case scenario, the village gets wiped out and you need to cure a couple new ones (after adjustments to the protection of course, usually just more doors for me so I get more than one golem). Curing is easy if you have the gold, potions, and a curing station.