Why not just play Animal Crossing if you want a neighborhood all to yourself without any social interaction outside a chat window?

Maybe I'm luckier than most, or maybe it's because I put a little effort into making my house a social venue. I do see my neighbors occasionally, especially since there's a large active FC in the ward that has several members I know from the server's hunt community and they're frequently running around the ward. I invite others to my house on occasion - we had gatherings there both nights of the JP FanFest for live streaming and sat around in the yard chatting about what was being revealed in. If friends go through Eternal Bonding, I invite them to use my house for a reception after if they want since it's next to the beach in Mist. And of course anyone is welcome to stop by and look around any time as long as I'm not in the middle of redecorating, at which point I "lock the door" to work undisturbed.

Certainly there's room for a lot of improvement in housing but I don't see your suggestions as a positive step for housing in a MMO. It would isolate players into a single player experience instead of increasing player interaction. I wouldn't want to see developer and server resources wasted on NPC neighbors that aren't real when those things could be going toward developing and hosting content that promotes player interaction. When I want a solo player experience, I go play a game designed to give it and not a MMO. MMOs are for the social experience.

If you want a better social experience from housing, it's up to you to make it happen.