I'm not really sure what you're asking here. Why do you need to unregister vRA from your current VCF integrated vRSLCM to an independent vRSLCM? You certainly don't need to deploy an independent vRSLCM just to keep using vRS products within a VCF deployment post v4.4.x
You can upgrade you current vRSLCM separately from VCF, check out this KB for supported versions: https://kb.vmware.com/s/article/88829
If I was in your situation I'd open a support case with VMware, stating exact versions of VCF & vRS products you have now and where you want to end up and ask that they provide you with the upgrade path you should follow (they've done this for me in the past).
Any reason you can't just upgrade to VCF v4.4.1.1 now as well (to ensure you're on the latest version) or are you holding off on more upgrades until v4.5 (or whatever version it will be that includes vSphere 8)? Personally I'd get current first - especially if your VCF is Internet connected so pulling down updates is trivial (I work in a dark site so updating is a bit more hassle).
vIDM seems to be the odd-one-out product in that you get stuck with v3.6.2 (I think that's the correct version, not in a place I can double check at the moment). I can't remember if I've applied any minor patches but essentially it's the one product that seems to have been left behind in the VCF world - I'm assuming there's a reason they don't support Workspace ONE Access yet (despite calling it that in their VCF documentation) but I'm not imagining there will be any significant vIDM updates before the transition to WSA happens. I'm not sure WSA is available as an 'all in one' appliance yet which is possibly the reason they've had to stick with vIDM.
We recently did a fresh v4.4.0 deployment and then upgraded to v4.4.1 before deploying vRSLCM v8.6.2 psp 2, patching it to psp 3 then upgrading it to v8.7 (bit strange but it was an 'on VxRail' deployment and we'd contracted Dell for v4.4.0). VMware's advice at the time was to stick with vRSLCM v8.7 even though v8.8 was supported - not sure if that advice has changed since)
