Switched

So this idea has been done before, but it's been in my head all day. So have a human Wormmon, Naoki! He hides his mouth a lot because, while he likes to talk, he hates people seeing his awful teeth and huge bracers. He loves cooking, cleaning, and video games among other things and is a huge sweetie.

Ken's Digimon form is based off of a deer, thus "Fawnmon." Deer are elegant and careful creatures, but can be incredibly violent and nasty when provoked. (As a New Englander, I'm thinking primarily of others in that same family, like moose. They can do a LOT of damage.) Moreover, dark!digivolved Kaisermon with galaxy elements and a huge, jagged rack of horns? Hell yes.

Odds are Ken would still be infected. The story in general would be a bit different- the Digimon's temperaments differ slightly from their humans', and the team dynamics would vary somewhat- but a lot would stay the same. An infected Digimon!Ken would probably still lose a close relative (Osamu could've been killed by enemies targeting Ken, if they were the same TYPE of Digimon), and could be convinced that Wormmon abandoned him. It's feasible that he'd do his best to keep all humans out, as he could defend the Digital World better on his own.