Now I get it.I mean, the external case for any sff psus, nearly like what seasonic did with their ATX titanium psus https://seasonic.com/prime-titanium-fanless, but still have space for a 92mm fan. The benefit for sandwich case is that air blown from bottom fans can't be block, it would go through the power supply and go up.
Which dimensions or compatibility do you have in mind? A case like that would almost be as big as a standard Sfx power supply. Except the airflow, not many advantages here I can see.
Wouldn't my Sfx to meanwell bracket be enough already?