Let's be honest, there's no way to balance the Vector while keeping it somewhat realistic. The RPM is already nerfed to 950 and 1100 from the standard 1200. I can't think of a single way in which to make it more balanced from the gun stat perspective. The gun has very low recoil IRL, maybe has some malfunction issues (idk how common those are), and is expensive.
Price of the Vector was already increased twice and as we can see that has no impact on people with 50m+ in their stash and BTC farm running 24/7.
You could remove 7N31 from the game, but .45 AP shreds too and AP 6.3 while not as powerful is still a beast.
Vector is a very cool gun, I like it a LOT, but I'd be lying if I said that I didn't see issues like this arising before they even added it, especially with the whole "ROF is king" in EFT. I think that its reached a point where its worse than the VAL ever was. Every labs game you get 1-5 people running that shit, basically every geared player is using either Vector or M995 HK.
There's nothing wrong with having guns fill a niche, or be better or worse than others, but when one gun is clearly outperforming almost everything else, in all situations, we have a problem. Regardless of how much realism you want, this is still a game at the end of the day and some balance is required to make it enjoyable and not stale.
my 2 cents.