If you "continue to come down off that figure" I would wait until your bodyweight stabilizes to buy such an expensive frame.
A frame's "stiffness" is more than mitigated by the right tire width at the right pressure. If your Aethos is disc brake equipped, you should be able to fit wider tires and run them at lower pressures, getting the comfort you seek at your current bodyweight.
If you truly want shorter cranks, seek out
Lennard Zinn's custom cranks.