Sounds feasible. I don't know if there is enough meat in a stock piston to cut that much dish and keep enough strength though.

Here's a different twist on the same idea... calculate and measure with stock rods and work with one of the custom piston manufacturers like Ross to design a custom quench pad piston. It could be a flat top plus quench pad. CR would be dialed in to target 9.5 by letting the flat part be a little below deck. Maybe target 9.2 or so to allow for cleanup milling of the head and block without exceeding 9.5. Leave the pad a little high like KB so the piston can be fitted to the engine by milling.

Ordered for one engine it would be a bit expensive but if you find some fellow "slanters" to go in with you and order several sets at once, I bet you could get a better deal.