Well, I don't like the idea of users picking the same nation. Festival of Music never allowed that, and it never created any problems. If someone desperately wants to represent a certain nation (even though it's a side edition, but alright), they should just put the registration date in their diary and make sure they book it on time. Besides, having the same nation appear two or three times will make things less diverse and probably more confusing.
As for the group scoring format... I'd prefer to have 3 points for the winner, 1 point each in case of a draw, and no points in case of a loss... That way the competition may go forward even if some user(s) fail to send their preferences on time. Additionally, I wouldn't like seeing users / entries getting diqualified from this edition. If someone fails to deliver their votes, they should still be allowed to vote again in the further rounds.