Great... Niki-84 then..

I doubt it would every be on that level. Four fast firing 20mm cannons with 150rpg won't appeal as much as four slower firing 20mm cannons with 200rpg for two and 250rpg for the other two with the bonus of each individual round hitting harder.
Remember, the Type 99 Model 2s are the second hardest hitting 20mm rounds in AH on a round for round basis, being very close to the Hispano II. They just have a low firing rate. That low firing rate coupled with 900 rounds of ammo make the N1K2 feel very friendly from a shooting perspective whereas the Ki-84, even if it were the Ib, demands high accuracy to be effective.