Ho-Oh, a Shadow Pokemon? If they had thought of the idea back when Colosseum was new and fresh, I'd have loved the idea. Anything to add a shade of mystery and maybe evil to Ho-Oh since I believe it's always been revered as a symbol of good in most media, especially in the anime. As for a bigger role, I agree with that too since it's counterpart Lugia literally "snagged" the lead role in XD. It would have seemed fair to feature both Pokemon in the main Gamecube games but the problem is it might have seemed too much like their roles in Gold and Silver if that were done. Kind of difficult to say for sure since either way, things would've gotten messy.