They would have to hire someone who can write.

New Vegas is a buggy mess that still isn't that stable without mods. It was the original Cyberpunk 2077 with how broken it was on release, and even though it has gotten reappraised and become a cult classic, it still has too shakey of a foundation to easily build upon. This is why visual mods are so limited in comparison to what you can pull off with the original version of Skyrim, which released the following year. They'd have an easier time ripping all the voice lines and rebuilding most of it in a new engine than hacking Gamebryo together with Unreal like they did with Oblivion. Even if they had the full source code, it probably still wouldn't be easy to pull off.

They will 100% just use AI, release complete slop and sell millions of copies.

Damn, am I gonna have to leave this community over all the NV glazing?

Cause this shit is getting fucking ridiculous.