So, you want to soft-fork-out of Segwit? Interesting. Because if everything will be done only in legacy space, and no additional commitment will be done anywhere (for example in the coinbase transaction), then it will reintroduce malleability, O(n^2) transaction hashing, and other problems, for no reason.
Part of SegWit is about keeping things backward compatible which has created a slight overhead. That can be removed with a hardfork and everything else including the malleability related changes can become the default behavior. For example what we call P2PKH right now could use the same sighash mechanism as SegWit v0 is right now without needing the overhead and definitely without needing the wrapped SegWit scripts.
we still need at least one year of nearly optimal consolidations in a hypothetical clogged up network to migrate most of the coins to quantum-safe addresses.
Exactly. This is why I support discussion about replacement options even though it is still too soon.