Long time no see guys. I might be out of the loop but here are my thoughts.
I feel like we first need to decide what the purpose of doing this is and what the process would look like.
I assume 4UC will just be added in the installer as a separate mod? So it's installed by the VP installer, but you still have to select it.
Therefore, what is the real difference between that and the status quo? To me, having it installed automatically seems like it really only affects two things:
1. New players who haven't already installed 4UC. If you've played VP for a while you probably already at least have 4UC in your mods screen, so literally no difference, even if you don't play with it. And installing it takes like 2 seconds.
2. A change of "ownership" of 4UC. Currently 4UC is more or less managed by pineappledan, but if it's part of "official" VP then much more power is shifted towards the community and Recursive, and we might make decisions with it that go out of Pdan's intentions. Seems like Pdan is fine with that? And, more work for the devs.
So for #1, do new players need to be shown 4UC in the install screen? I'm not really sure. You can argue for or against it. My preference is that new comers to VP aren't bombarded with too many changes from the base game. This many abilities and units might be a bit much for a new player to handle. I especially feel like base VP is a good way to start the game then 4UC once you want something new. But it's very debatable, I could go either way.
For #2, it seems like doubling the amount of UCs is a lot of stuff that could lead to more management/bugs. Of course, pdan has been managing it well so far, so you could say that as long as pdan keeps support that's fine, but it leads to more work now for recursive and any other devs as 4UC is now a part of their responsibility as well.
So to me those seem like more important considerations than "balance". These two factors will affect the long term success of this mod -- if we don't have new players, or devs have too much work, then the mod could die. That is being over dramatic, it's not like 4UC integration would cause VP to die. But I'm just saying these aspects matter more than balance, unless it literally makes the balance unplayable, which I don't beleive anyone is saying.
Both of those points #1 and #2 go slightly in favor of not integrating 4UC. #1 is debatable, but #2 is certainly true, although the magnitude of how much more work is needed is debatable. That being said, if you can argue that the work is not much work, and there are some benefits to having 4UC in the installer (can someone specify these?) then a vote yes is reasonable.