The situation is pretty much like importing data from a non-PDM environment, into PDM.
This is how (i think) i would have done it:
In vault1 view, check in all.
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Remove vault1 view, keep local files
Create vault2 view
Copy all local files and folders in vault1 folder into vault2 view
Rename vault1 folder to break reference paths and avoid "outside PDM" warnings
Check in and verify check in dialog in vault2
But i would test it small scale first
Good call it worked perfect. Thanks!