Good question. But realistically, a mod like that would also need an installer software able to pull and convert also: textures, meshes, game plugin data, scripts (and perhaps some other misc stuff I overlooked), or creatively recreate some of these from scratch, or have permission from Bethesda (against the company policy, I am afraid).
In practice, Bethesda does not permit mods with assets from a different Bethesda game. Everything else is negotiable, there are kid toys trains turned into Skyrim dragons, but mods with assets from another Bethesda game (or even from a DLC of the same game, but without making the mod dependent on that DLC) are taken down.
So, modding projects which plan to accomplish that with some installers extracting those assets tend to operate a bit under the radar, legal gray area or not.
I don't know if Skyoblivion ever managed to write a robust solution for translating the codebase from the old scripting language to Papyrus, and I can see why it might be a huge hurdle for modding teams.
To clarify, I was only talking about audio formats. Not automagically converting everything to run on the new engine. Doing that would kind of be missing the point.
There is a similar project redoing New Vegas in Fallout 4 (F4NV - I'm not affiliated with the project, just a fan snooping on their progress from time to time) and one of the really important things is that they're making their vision of what NV could be. This means all new meshes, textures, and code - not the old content updated to run on the new engine.
I've written some code for fiddling around with the plugins the engine uses (.esp/.esm/.esl files). The basic structure hasn't changed, but a lot of the records and fields have. Automatically converting them well enough to not need manual tidying up would be a pretty arduous task.
Converting the old code into papyrus would be as well.
