I’m much more excited about the SwiftSync variant that makes less assumptions than -assumevalid. Would love to try a demo of that… SwiftSync - smarter synchronization with hints · GitHub
Maybe implementing this as a -reindex is easier for a PoC, since you already have the undo data on disk?
Regarding MuHash performance, have you tried with this? Add ASM optimizations for MuHash3072 by fjahr · Pull Request #19181 · bitcoin/bitcoin · GitHub. Though I guess this one https://github.com/bitcoin/bitcoin/pull/21590 added much more performance boost, and is already in your branch. One comment in that PR suggests there’s more potential gain: “Using libgmp for inverses is 1.5x-2x faster still”