We have to be realistic and acknowledge us has not only veto right but massive influence, we should focus on integrating Ukraine into the European Union / Economic Zone. Nato is a defense alience so it would be complicated to figure out how it would work to let in a country at war (or with occupied territory in case of a cease fire), but strengthening economic ties and pro-actively implementing eu regulation is very achievable even for a country at war. The Ukrainian economy is so wrecked it will need long-term support anyway, I figure this integration will happen whether Putin likes it or not.