What the Omnitrix allows the user to turn into per canon

The only requirements for something to be in the watch is for them to be sapient, have DNA, and not being magic based entities (thus why it not having Anodite/Stone Creature transformations).

So the watch wouldn’t allow the user to turn into a Gem from Steven Universe since they don’t have DNA but it WOULD allow the user to turn into Galactus (since he not only has a kid but has been cloned) and a 5th dimensional imp (seeing as Superman 1 million has the powers of one since he has all the powers of his descendants somehow).

The magic portion would mean that it would allow the user to turn into magic users so long as they aren’t powered/sustained by just magic. So various entities from Harry Potter are fair game (like House Elves/Mermaids etc).

As shown with Nanomech any species tied to a hivemind is made to be uninfluenced by said hivemind (so something like Prototype’s Blacklight wouldn’t have to worry about the viral hivemind for example).

As shown by Alien X esoteric DNA isn’t a problem either seeing as Celestialsapiens are WoG to exist across time simultaneously being 5th dimensional entities. So afaik Time Lords from Doctor Who are likewise fair game.

Seeing as fictional exploration is predicated by the fictional golden rule (that is everything is like real life unless specified otherwise) any species that isn’t explicitly said to have DNA but match all the other criteria are likewise fair game for being scanned and made a available transformation. Also as I’ve pointed out before in my debunk here, all transformations are based on the base state of the user and are in no way the peak of their species unless said user is also the peak of their own species.