I see exactly the opposite.
With the freezer I can have very rarely occuring failures, due to
freeze ordering effects.
And without the freezer I have a 100% reproducable problem, that is
not hard to fix according to Alan Stern. OK, I don't know what the
next problem would be, but the powermac experience shows, that it's
not nearly as bad as you and Oliver try to make it out.
It cannot be just worked around in fuse, as a task might be sleeping
on a number of VFS mutexes as well (i_mutex, s_vfs_rename_mutex, etc).
It would be a gigantic hack, possible at all.