Has anyone here had experience with cavity sliding doors in ICF walls? I can see it would be a challenge, but would love to work out a good way to incorporate them into an ICF house design. Thanks

I think the amount of work and material needed for this doesn't make sense economicaly.
Some ideas look better on paper!!

but would love to work out a good way to incorporate them into an ICF house design

I'm not very familiar with them, but why would cavity sliding doors be any better for ICF construction than swinging doors?

I don't see where you live in your profile so this approach may not be easy to do in your area, in Florida many exterior sliders use a track system that goes beyond the door opening on the exterior of the home. The door panels stack in front of each other as they are slid to one side. The extended tracks allow the door panels to be slid in front of the exterior wall providing an unobstructed opening.