The upgrade Paths the OP laid out are not legit Upgrade/Downgrade paths as you can not change x86 to x64 during a migration. If you had an Win 7 X86 system and you purchased an Upgrade to Win 8 you would get Win 8 x86 only via download purchase.
Now, there are ways to change to x64 from X86 using an upgrade disk, but they require a fresh OS install and not a system migration. So partitions are not an issue, as they will be deleted and recreated if needed.
The same is true for a downgrade from win 8 to win 7 or back to x86.
I'm trying to figure if there will be any issue with that limitation and will it affect anyone long term.
I've no time for testing my curiosity out like in the past, and hoped someone might have been able to pass on knowledge on the restrictions and if it could be of concern in certain instances.
