Despite the breakup of the USSR, I don't think Russia would have let that happen.
For comparison, How do you think that the USA would react if Turkey tried to size control of US nukes housed there?
See for instance where that was built: https://en.m.wikipedia.org/wiki/R-36_(missile)
Also, Chernobyl.
The answer is probably because the alternative was too scary for the west. Better to keep dealing just with Moscow.
No it wouldn't.
They were pressured by the US to give up Soviet nukes. Codes are easy to fix, but nukes need service and are expensive to keep so it was as much of sparing measure than anything.
If Ukrainians wanted they could have prevented this at the time of Soviet Union dissolution, but they didn't so there's not much to discuss.
My point is basically that if Ukraine tried to take full control of the Nukes in their country, they would have been picking a fight with Russia, and possibly the US as well.
https://www.washingtonpost.com/archive/politics/1992/03/14/u...
https://www.jstor.org/stable/resrep10926.13?seq=2#metadata_i...