No to hp on doors. Would just be another mechanic suited towards zerglings. A lot of MO2 is already zerg friendly, from PvP mechanics to PvE(Boss farming).
Using houses to hide is the equivalent to zerg guilds/alliances running back to town into the GZ to hide. Only difference is the zerg has more than one exit/entry and can muster up more numbers within town, while the little small trolly boi groups don't have those luxuries. The PvP right now is boring, there's not much to do, so majority of people sit in town afk or roleplaying all day. Only way to get PvP is have the off chance you run into someone into a dungeon, or you poke a town and use hit and run tactics, to avoid the zerg build up.
SV shouldn't of added housing or keeps on release, without sieging. Then we wouldn't of had the issue of uncontested keep building, using cheesy unintended methods to get keeps up early and house hoppers wouldn't be a big issue either.