If this method will be tested by FedoraQA, then I believe this upgrade method
can be safely recommended to user.
The feature owners of this need to do the testing and prodding, not QA. The
way this feature is written, it seems to imply that QA is supposed to
implement this feature.
Note that this doesn't fix problems caused by dropped packages, that block
other packages from being updated. One possiblity here would be to create
a special package that obsoletes all of the dropped packages from the
last release (or two depending on how far back you want to yum update from).
There are going to be some releases where you need to do things outside of
yum to upgrade. I don't know that we want to advertise this as a feature
when it can't really be supported from release to release. However, a group
of people who wanted to report bugs for missing obsoletes and the like
would be appreciated.