Well what if it were a really large house? Maybe everyone could have their own flat, almost, but with something like a common room for everyone to gather in? Only it would be a common room where it was all our friends, instead of just your house mates (so you'd never have to see Finnigan and I'd never have to see Zabini.)

But you're right about the security concerns, unfortunately. Sort of spoils the fun of imagining it.