Ah, yes, I know (usually sash) big box window units hanging out of
windows, but not what I had in mind.

I mean exactly as current "split load" units except the internal box
is mounted externally, weatherproof, with just twin 9" vents to the
inside.

No hoses, high reliability as no "self-seal connectors", just two core-
drill holes. Exact same form-factor as existing systems - just a
different metalwork box, internal grill with IR remote receiver,
minimal R&D.