I too think this is probably way to much deflection for something as rigid as clay tile. Not being a fan of OSB in general I would probably stiffen the floor with an interlocking jointed wood floor if possible (yes it is more work...but stiffer) and this is pursuming that the frame work can take the added weight.
I have never seen tile suffer well any deflective attachment surface as you just described.
Now, on a positive note to your idea...no guarantees here...I can share a few proprietary concoctions that my mother used and I have experimented with that give good results and may just work with this much deflections...You are going to have to make your own test panels and do a bit of expermenting.
Both of these either used "sawdust" as a "matrix filler" or "cork granules."
I don't know how permie it is but you can use clear silicon and grout powder. Fill the grout lines with the silicon. Then take and dust the top with the grout powder. Let silicon dry, then sweep/vacuum up all the powder that didn't stick to to silicon. I've done this around thersholds where the tile grout line and therhold meet. I don't know how it would work over an entire floor tho.
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