If we’re going by story I feel it’d be either Rig, Hayate, Hitomi, Leifang, Kokoro, or Eliot. Everyone outside of Rig either came close or has progressed in their tourney grind enough to garner interest in them winning.
Rig would probably be to draw in at least one of the ninja’s, maybe Hayate. He’s the only ninja to not technically win a tournament. So it would be for that reason for Rig or Hayate.
But Hayate has expressed pretty openly that he's "not interested" in DOA, so why would he even enter? I think the ninjas in general dont enter DOA anymore, they are there to fight MIST. Rig has a good chance of winning, being Jann Lee's rival. but I dont think he enters either. The ones that where in the finals, Kokoro, Eliot Leifang and Hitomi one of them should win...one of them being...Kokoro