Information around Altavault is limited....But, I think there is 'virtual altavault' (software version) which you can spin-up/build and then use it to connect to s3 (may be). I have no idea but try to look up for info. I will see if I can find some info.
All I can say is - you are heading in the right direction. It's not easy to get help on AltaVault as far as documentation is concerend, b'cos most of the TRs on AltaVault has been taken-off from the web. I had one saved, so I am attaching it here, take a look if you could find anything useful to your scenario (Section 3.1 ?).