I am super fussy about 480p so I removed the need for any scaling by using a 480p LCD TV (20" Philips, over VGA). Details in another thread.
That’s the reason I didn’t get WiiDual in the end, because I don’t have a 480p HDMI capable set (actually I do have one, but it messes with the image - the only truly unmodified image is over VGA).
I’d wonder how good or bad your scaling is before trying to beat it?
There are Panasonic 4K TVs that do quad upscaling of 1080p but I’m not sure how they handle 480p.
Sorry to not really answer your question!
And welcome!