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Honestly, the idea of a Digimon/Pokemon crossover could work, it's just a matter of figuring out what kind of game it should be.
My idea: it takes place in Kanto following the events of Sun and Moon. You play as Lillie going through her journey to become a Pokemon trainer. Suddenly the Pokemon PC system becomes corrupted with a Digimon virus, and she goes into the digital world to find the problem, and meets a Digimon tamer on the other side.
Instead of being a traditional Pokemon game, it could be a dungeon crawler thing. The Digimon tamer recruits Digimon to help along the way, and as you rescue PC boxes, you can "rent" Pokemon to use on your quest. Lillie herself starts off with two Pokemon (Clefairy and Alolan Vulpix) who can be trained and evolved as the story progresses.