We had the same sort of thing going in Council of Wyrms, and it ended up only one person decided to be a non-wyrm out of 17. I doubt it will be a problem, but we shall see... as far as game balance is concerned, observe what happened when the will of the council turned against R'lyeh in CoW. I wouldn't like to be in the "dragonslayer"'s shoes or scales or whatever as the arrogant one who wants to wreck our RP'ing fun. Plus it will give us senators something fun to do besides bicker with one another. But if it ends up more than half non-dragons, I agree we will have to put the house-rule foot down just so we can have our theme.
I imagine the non-dragons will have to make a "coalition of the meek" in order to survive
I still haven't decided on a nation yet, but I still would like to play (as a dragon).