Has been proposed thousands of times, but why not?
I know their purpose is for guild-use only, but to be honest, nobody follows that RPG rule. So why not use it like a "Guild Hall" where you can show to the public your guild's identity, or just a bigger and better-decorated house. Seriously, we paid 5$ for it to be invisible to others. Of course, making it public is completely optional. I don't see any contradiction with this idea, other than imaginary RPG rules.