Just my opinion of course, and I apologise if it sound harsh.
To me it sounds like a classic problem creation exercise!
The solution is to tiller the bow properly, if you deliberately miss-match the limbs it's probably going to make tillering more difficult or at least more counter-intuitive.
If there is a problem with tillering... there will still be a problem with tillering.
To be fair, we all have some tiller shift occasionally and that's why why shoot bows in.
I just had a flight bow I'm making shift on me and the lower limb suddenly appeared way too strong, because I'd made it slightly too strong and it started overpowering the upper limb. Fortunately I'd allowed a couple of pounds over weight and a few scraped brought it back in line.
Mind if you want to make a bow with two different species for the limbs as a novelty, or character bow, that's different. I just think it will make the job harder rather than easier
Del