I think w are over-engineering a workaround for something that could be part of system-upgrade. See my proposal in https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/DQZOCSVPW4R4MZR2QYBQTO6ZTTU3RCKW/ that got 0 replies:

Generally, I think we should instead strive to have configurable bahavior of dnf system-upgrade:
....SNIP
Such solution obviously requires somebody to design it, code it, test it, support it and maintain it. I cannot speak for the software management team, but I guess they would have reasons not to do that (such as capacity reasons).

DNF team has its priority list already packed. I think it make sanse to do this designing phase in separate tool. And only when it becomes obvious what we want and how to do it, only then merge it to core DNF code.

Miroslav