It is hard to say what will happen now that Bethesda is part of Microsoft but Bethesda explicitly approved the reverse engineering as long as they do not actively advertise the possibility to use it to run their games on mobile devices.
Are you thinking of Nehrim? It was made by the (mostly) german modders of SureAI, just like the skyrim total conversion Enderal and earlier Arktwend and Myar Aranath for Morrowind. They have been pouring lots of resources into this for a long time now. The Morrowind and Oblivion remakes for Skyrim are coming along nicely, give the development videos on Youtube a try (Skywind and Skyblivion), they have also hired some of the original voice-actors.
Thinking back 3D packages and motion capture were really expensive 15 years ago. Now everything needed to create high quality content is somewhat affordable or even free (Like the giant leap of Blender to Version 2.8).
BG3 with its fully animated dialogues does produce quite a lot of effort for a bit of dialogue but it is nothing the modders cannot handle... provided enough access to the game. I hope that Larian take a look at the very positive experiences of Bethesda or THQ Nordic (Gothic 3 only became a good and stable game due to mods) in opening their games for mods.
