Regarding a possible arena, I think something like
Rogers Place in Edmonton would do really well on the Flats, mixed in with other buildings, and possible connected directly to the LRT station. Also, I agree that a hotel would make a good compliment to the area/arena.
I'm just hoping some external (outside of Ottawa) consortiums take a bid at this project. Ideally, given it's magnitude and relevance to Ottawa, I'd love to see a bigger name international architecture firm get involved.