NEW IDEAS FOR THE DIGIFORMERS AU (cos I keep changing stuff for it and currently the only character arcs that are set in stone are Sky, Star, Soundwave and Jazz)
So... rather than Optimus being a digimon I was thinking of making him one of the Digidestined. He carries the crest of Hope cos I can’t think of a better trait to embody OP.
His digimon used to be Megamon (who I sort of have been imagining as a BlackAgumon in his rookie form). Optimus was one of the first kids ever to travel to the Digital World and he’s been there the longest (and thus got the nickname of being ‘the Prime kid’).
The two of them were perfect partners but eventually Megamon started to change, becoming more obsessed with power and eventually turning evil (oh noes! I still have to figure out the details maybe I’ll make Unicron the final villain and he affected Megs). After that point Optimus left and took a Bumblebeemon as his partner instead, probably rescuing him after Megamon attacked a Beemon village.
Since Optimus left Megamon has never been able to reach the same level of power. However, he still keeps searching out ways he can get to the higher levels again, but now tries to recruit new human partners to join with him to reach the same levels of power.