Thanks for the link Heather_Poulsen.
jvintzel- I may have been a bit leading suggesting Endpoint Configuration manager should contain this capability as that is what our customers are using so would be easier for us to implement.
The reality though is MSIX AppAttach may necessitate significant changes to the Config Manager client as it currently processes the user policies after the user logs in, whereas for AppAttach I'd assume you'd need to intercept the user login process towards the start of login to attach the MSIX VHD before the login has completed.
Even if that proves difficult and support does not make it to Config Manager I think something is needed for allowing use of AppAttach away from AVD. We have customers still using on premise VDI solutions and may continue for some time and whilst MSIX is advancing in terms of capability and reliability without AppAttach support those customers are still considering roadmaps which take us away from MSIX completely as speed of app delivery at user login to those non persistent VDI's is a key requirement.