I'm the sprite artist formerly known as Digi-Brigade
For me, CresGarurumon looks like Shutmon + Duramon.
I am a Digimon fan who was an Elementary Schooler during WarGreymon era,
a Middle Schooler during KaiserGreymon era, a High Schooler during ShineGreymon era,
and a college student during ZekeGreymon era.
CresGarurumon's chest however resembles Jesmon a bit too much for my liking. It is a common design similarity in recent Digimon but I think even Jesmon has that crystal in it's chest. CresGarurumon just looks all sorts of clunky.
My Evolution lines:
I'm not sure why that's relevant. If anything, Digimon and Appmon would be more likely to get integrated evolution lines in a card or video game than they would in an anime.
Hell, N0 outright admits that several of the characters that appear in it don't belong in that universe and have no reason to actually be there, the most notable examples being Shoutmon from Fusion and Meicoomon from tri.
I'll work to see that justice will be fully served, meow~!
That's relevant to the franchise as a whole, I suppose, but not relevant to having Digimon and Appmon in the same evolution line. They've already appeared together in something. There's no reason future media couldn't have them evolve into each other.