The state of Switch ROM hacking is we can rip apart games quite happily and any hack worth speaking of can be made for total control -- there are no 360 DVD or 3ds' sky3ds style needing region compatible 1:1 games. File formats have been similar enough to everything before it for years now that while there might not be tools for a given system/format if you have reverse engineered any format you can probably hang or get up to speed quickly. We don't have the best debug or emulators to play with but that does not stop too much -- the vast majority of formats hacked on anything with a file system have been static analysis and maybe tweaking some things to confirm it as working the way you think on hardware.
I don't know of any specific projects but unless they were noted here I likely would not. I don't tend to see such games get messed with (console wise Phoenix Wright has a bit of a hacking scene, and maybe some people playing with Fate, but not much else on the visual novel front) but there is still the odd isolated community here and there doing their own thing.
There will be three possible avenues here, bearing in mind I don't know how the PC stuff plays out for this one. All this should go regardless of whether it is the classic BMP and wave audio affair or a more refined approach with actual animations and whatnot.
1) The files are in place on the game already and just need activating by flag or something akin to it. Can we say incoming hot coffee 2.0?
2) The files the console port uses are the same (or near enough) to the PC that they just need to essentially be copied over. Could go either way but as time drags on and consoles gain more power then we are seeing more and more PC ports/sticking with "common" file formats rather than custom from the ground up to match/work quickly with the hardware.
3) You get to figure out the formats of the port and the PC version and go from there.
The rarely seen 4th (at least as far as visual novels are concerned) is the PC game uses a format that an emulator/interpreter/engine port can work with. We have seen dedicated visual novel engines dealing with known games as far back as the DS (possibly further if you want to consider SCUMMVM's various ports) and out and out ports of individual games further back still. Don't know what, if anything, is available for the Switch at this point but I will note it anyway. For more conventionally emulated games then we have long seen homebrew efforts surpass the commercial ones (the GBA having many examples, and the PS1 possibly even having a few), indeed injection into commercial emulators was something not new (see animal crossing or Zelda on the gamecube for a previous well known version) but strange when it cropped up on the 3ds.
