These are good ideas but the net result is not too different than what I'm already implementing as described above. The difference is that having to get a petition signed before you can have a town means that there is more opportunity for adventure, etc. as you try to get all of the signatures that you need. Besides, requiring a vote of confidence from the players is not a bad thing and if you instead travel the world enough to get enough NPC signatures well then I don't mind giving you a town of your own either.
Once you have a town you can place sites down for specific types of buildings and NPCs will come and build that or move into whatever you've already built. But if you've built it or placed it in a bad site for it (like a dock in the middle of a field) then no NPC would ever want to go there.
Also, something to remember... in general the property system doesn't keep you from building anywhere you want. It just grants you protection from others wrecking your stuff. Assuming there isn't already some bit of property somewhere then you can build whatever you want... it's just that the next guy might come tear it down again. The property system gives you some assurance that your carefully collected resources don't walk away.