I think it sounds nice, but the thing is that I only did 3 or 4 megacampains til now (CK2 -> V2) but ultimately it was always kinda boring. Converter-generated worlds have too many flaws, and they are paradoxically too generic. And there are two many lengths - 2-3 useless centuries for CK2, and since you already have a strong empire when you convert to EU4, it's the same thing in EU4. In V2 the world is divided between several big superpowers and it's just extremely boring from the start.
So for me it's one of those cases where the very idea/perspective of being able to do it, or to imagine it, is vastly superior to the feature itself. It's a bit like how people tell themselves stories about their space empire in Stellaris or decide to conquer the whole world in EU4. Maybe you'll have fun doing it once, but generally you'll need to force yourself, and share it on social media to have a sense of accomplishment. You don't really enjoy it.
How many people here can say that they already did fill megacampains and enjoyed every part of it? Or even enjoyed it globally? I personally have much more fun in Paradox game when I pick/create a country on the map, then decide to see what happens or set my own goals... only to leave the game once nothing interesting will/can happen. I can't deny I enjoyed converting my CK2 Yazidi Malian game to EU4 and then to V2, or the one where I formed the Zuni empire in CK2 (was kinda proud of that one since it was Ironman), but even if I have nice memories, I also remember needing to wait for eons while doing something else. And what did I get in the end? Some screenshots few people looked at, a bit of satisfaction... In v2 it doesn't really offer interesting stuff to do. I literally forced myself to play just to have my own personal empire in the game...
So ultimately, I don't think that making a converter is really worth it, even for the players. And for the devs it sounds like a waste of time and ressources. But what would be nice are a random world generator or at least a "nation customizer".
There are many gameplay elements from CK2 that aren't translated to EU4 with the converter. If such a converter is officially supported you can be sure lots of EU4 stuff will not be translated into Vicky3, and also that some stuff will be generated in Vicky3 (like political parties or whatever features V3 has).