As I have stated, this could open inter village relations to the likes of the Glacier and Storm secret chats and beyond. And remember, Sun can go anywhere it wants and mingle with everyone, thus making it, of all nations to form a strong bond with, very important and outweighs it's size some. Another factor to remember is that Sun is small, yes, but we have no real allies on the site. And it might behoove us to know we have one village that supports us because in the outbreak of a war, we can know Shadow and Mist will ally each other in great Haste, and Glacier will most likely not come to our aide but remain in a state of slight neutrality. Giving us Storm, which even though we made it big, it has no feelings for us that are overpowering and so far I can't see it being an extremely reliable friend. Would it not be safe if we knew we had one ally?
Another thought to incur, is even though it's small now, would it really be all that doubtful that it could indeed get big? And once it is big; problem solved there. I believe it smarter of us to ally with Sun and help support it now, then to wait for Shadow or Mist to snatch it up from us and let them instead make it strong.
Just a few reasons why.