First, Avast Team won't tell you to clean install unless there is a reason. This was not a general recommendation.
My comment was that SOME users that had SOME type of problems decided to troubleshoot, without apparent success, but cleaning all and installing anew worked for them.
About the image, I understood it perfectly the first time. You were still going back to have the same "past" versions, registry entries, setups, older back up copies of the VPS and so on.
The possibility to back up Avast's settings has been a desire / hope / wish / feature request for a long time, so I understand your point about it.
The complete VPS for complete download so to update an off line system is, as you commented, currently not working. It has been "retired" until they correct the problem.
For future reference, when you have a particular problem with one definitions update, while you KNOW that it was working before, usually it is "naturally" resolved by some simple alternative procedures, like for example:
_ simple reboot;
_ wait until next definitions update is found;
_ repair of avast and reboot;
_ installing again over the current installation (no uninstallation needed) and reboot;
_ other additional solutions;
(those are "or" procedures, not necessarily "and").
So returning to a previous image, or even a "clean up" are more for impatient cases in MOST situations.
I'm glad you have your system working now.