boost-1.73.0-4.fc33 is building now:

Building boost-1.73.0-4.fc33 for rawhide
Created task: 45462220
Task info: https://koji.fedoraproject.org/koji/taskinfo?taskID=45462220

I've also pushed one extra fix to freecad (just adding to your new
patch file). A test build with the new boost and that extra fix
succeeded, so once boost-1.73.0-4.fc33 is in the buildroot you should
be able to build freecad (I am going AFK now, so won't be able to kick
off the freecad build myself).

Once the boost build completes this will tell you when it's in the
repo:
koji wait-repo --build boost-1.73.0-4.fc33 f33-build

And using --enablerepo=local will let local mock builds use that new
build.

I'll check email again in a few hours.