Arcade ports were technically impossible for 16-bit gen consoles bitd, but we got lots anyways. Shovel Knight would be less of a stretch for MD/PCE from what I've seen. If some sections only have 8 lsyers of psrallax instead of 12, it's not a big deal. Playing a game on real 16-bit hardware with chip tunes would be a big deal though.
What I saw in preview videos definitely looked beyond all existing and potential-within-a-few-more-years NES add-on chips, but not unreasonable for MD/PCE. If ports were handled by typical average 16-bit gen developers with tunnel vision who can only be bothered or are only capable of scrolling tile layers in uncreative ways, then yeah, they'd need a PSX/Saturn. Unless I never got to see some particular parallax examples in SK, then a reasonably facsimile could be pulled off that wouldn't look different to the average person, unless they compared them side by side.
The idea of playing a modern computer game with faux retro dressing on modern hardware doesn't appeal to me. Playing even a compromised version on 16-bit consoles would be completely different.