To add an AC outlet, for example, you just drill a circular hole in the wall, tap into the wiring, add the outlet and you're set. If you don't want it, pull it out and plaster over it with more earth to seal the hole.
Dave Sim said in his latest thing of his, 'when you're on the right track, you'll know it, but until you get there, you have to believe you're on the right track'. Interesting little conundrum. It's not easy.

