I kinda like Kommo-o's design. I think it looks cool.
Personally I don't think Dragonite really needs anything right now. It has among the very best movepools among all Dragon types, a great ability, and good stats. But then again, neither did Garchomp or Salamence and they got Mega Evolutions. Hydreigon's a bit in a similar boat. It's a bit faster than Dragonite but has worse offensive stats and it lacks some moves in its movepool, most notably Thunderbolt (although it still has a great movepool). I wouldn't mind it if it got a new Z-Move or something.
Goodra probably needs something, it's a bit similar to Kommo-o, just with the bulk more focused on the special side and only one type. They've got similar offensive stats, a similar speed, and their movepools are both good but not outstanding. Goodra can do a rain set with Muddy Water, Thunder, Dragon Pulse, and Rest with Hydration for instance, it's not without options. Yeah Goodra could probably use something like a Z-Move to give it an extra push to really become great. I wouldn't like it if it was on Sludge Wave though, I think it should be on something it learns naturally. Maybe a Z-version of Rain Dance.