Wow- that is WAY more complicated than I thought it was going to be! However- great input and it is much appreciated.
I think the bottom line is 13.6mm more posterior positioning of the saddle compared to the Diverge- and I definitely do not have that much available clamping space with my offset post. So- I would need a zero offset seat post to correct for the change in saddle in relationship to the BB if I were to opt for a Waheela.
I have never purchased a bike without riding it, and I am sort of getting the vibe that is still a good idea as all this geometry stuff is only part of the equation.
Again- thanks for the insight on frame fit calculations.