You can see for example here: https://github.com/taprootactivation/Taproot-Activation. As far as I know, only the biggest pools were contacted for taproot support, there were no solo miners having some significant power. That means even if your proposal would be backward-compatible, you would ask big mining pools for support, not some independent solo miners. Of course you can rely on solo miners, but then I expect you wouldn't get more than few percent of the mining power supporting your version.