Dynamic imDisk and image-load (VHDx possible ?) at startup/Save at shutdown. Possible ? If yes, How ?

[Wizard]

I wonder if I could have imdisk load a vhdx as image at startup, and save/sync it at shutdown ? If not vhdx, perhaps another format ? Tried setting that in RamDiskUI, but it just seems to ignore it ?
PS: I my case, everything runs as NT AUTHORITY\System