I was actually thinking earlier today about writing an addon that would record inventories in a digestible way. CSV or whatever.
It would have to be an addon, as Blizzard’s web API doesn’t, as far as I know, have a means to see guild vault contents. So they would have to be acquired via gameplay.
TSM does a “phone home” thing where a separate app decodes Lua savefiles and sends it back to home base. Probably that would have to be the approach, except it would be local to the user’s PC only.
Be grateful for the effort your gaming service provider has given to your concerns, and have a great weekend!