Well the presence of Ki-67 isn't going to ruin this setup, it just seems to be a bit much, but I realize the current alternatives are slim.
And brady is correct that if compared to a Boston, the speed, and bombload of the ki-67 are pretty even. It's the defensive armament that gives the Ki-67 the undue advantage in the bomber role imho. It can be a real ack machine if you don't make smart passes on it. The Boston (not A20) is fast but pretty much defensless, but historically that is correct too.
The Ki-67 in this setup is supposed to represent the Ki-21 sally which was the predominant bomber for the Japanese over Burma. So from a historical standpoint the Ki-21II sally was 30 mph slower than the Ki-67 and it's defensive armament consisted of 4 7.7mm type 89 mg and 1 12.7mm type 1 mg where as the Ki-67 utilized 12.7mm guns and a 20mm cannon. So if you look at it like that then there is a pretty big difference between the substitution and what was actually used over Burma in the late 41 time frame.
But if you look at if from the point of being balanced then yes there is not much else that can be done unless you dropped both buffs from the setup and that would just spoil the fun for the guys that do enjoy buffing.
Not much we can do except make smart passes, which after all is what we should be doing anyway.
Cya over Burma