[Kiwami]

At first I thought "sure". But the more I think about it...

Amazing Mighty, to me at least, is more of an accident than a real form. A forced tap into Kuuga Ultimate, crammed into a vessel which cannot possibly contain it.

It was just accessed through the Mighty form and isn’t necessarily a direct upgrade to it. Maybe it's more of a missing link between Kuuga's separate forms and Ultimate form.

On the other hand, if it is a missing link then maybe it is also logical that that link, this desperate action of unlocking Kuuga's true potential can be achieved from multiple angles, each being different depending on from which form it is transitioned into. So technically they could exist, practically I’d say because Mighty is the most balanced and natural form for Yusuke it's the only way for him to access an "Amazing" form.

So Riku might've done it, Yusuke could've on paper, but was ultimately unable to. That's my take on it lore-wise.

Speaking real world? Like, making the show? I think it would’ve been terribly boring if they deiced to take time to feature black-ish upgrades for every form. They already each got one upgrade with Rising, that’s enough IMO.

By the way, great topic. I never thought about that to be honest