I'll not argue with your engineering experience or the amount of thought you've put in on this, jmillerfo. And I agree- my cabinet has not seen more than 45 degrees C even with ABS. Still, the power supply would prefer a cool environment over a warm one, I suspect.
For the MK3, if you look at the Lack Table Enclosure and Power Supply external bracket, it's a pretty easy split to accomplish. I used (and swear by) Anderson Power Pole connectors for a clean buildout.
As a result, you can quick disconnect the printer from power supply for servicing. Or simply remove the cabinet, disconnect the fan cord and the printer and power supply come off the lower table, still connected, one in each hand.
A lot of what we do with these builds is not an issue of right or wrong as opposed to "because I can" ;-)