I second this approach in fact I think some of youe screenshots might have been what inspired me to get an OSSC. Now I like to force widescreen on some 4:3 games that support it well enough too, pretty nice to be able to switch back and forth.
Twilight Princess 4:3 to my CRT Monitor at 480p:
OSSC passthrough to 4K TV with light scanlines:
Line 2x OSSC with scanlines:
Twilight Princess HD Remake 4K TV:
