in the campaign, I encountered several "champions" of empire factions that i think were not intended to be champions. Kraxis had a "Karavox Honorguard" who behaved like a champ (didn't get killed but got a weakness/wound on the after battle victory screen); likewise, Magner had a Pioneer ( 3 figure unit) that was also flagged as a champion (was a bit hilarious - a 3 figure champion Pioneer with battle axes and  horses) and resoln had an "elder cyndrum demon" (i think) that also functioned as a champion; this one had broken visualy since the AI put it on a horse and the model of that unit didn't really work with a horse. 

i guess those guys were all bonus starting units of those factions and somehow got flagged as champions instead of regular units. let me know if you need a save to reproduce - i made a separate save for the 0/0/0 yield Magnar capital; Kraxis and Resoln are already dead at this point, but Magnar is still alive, so the funny champion pioneer should still be around in that save game (probably immobilzed in one of the cities i haven't conquered yet)