Yes, a Mayor can abuse the Revoke power. In this case, it up to the player to be careful what they spend their coin/time/resources on, really. I was thinking of an Auto-Revoke after 1 real week and remove the Revoke power from the Mayor but the Mayor could just ignore it and not Approve it and let the Auto-Revoke do the deed.
This situation ties into my general philosophy for V6 that players need to police themselves. If you get screwed, learn your lesson and make adjustments so you don't fall into it again. If you don't like the mayor, wait until a new player gets that mayor-ship or go find a different town to work on. It doesn't mean I will ignore potentially abusive things like this but I would rather players deal with it themselves.
Guilds could become the driver for making towns but I like them separate. Guilds could abuse their power and privatize a town, blocking outsiders. The whole point is players building publicly accessible shops/areas for all to benefit. But allowing Guilds to build town-like areas should be allowed too but Town land and Guild land should not block/restrict each other. Not really sure how close Guild in V6 will be like Guilds in V1/V2. Time will tell.