I was a Unitarian Universalist for a time, but then I came back to believing the way to God is only thru Jesus. This was because, to me, in addition to repentance and forgiveness, Jesus is the only Way that was truly personalized to each individual, meeting emotional and physical needs in this life and in the next. And I learned about CEU.
Not every disbeliever is a horrible, evil person—anymore than the rest of us sinners anyway. A lot of the people I met have serious problems believeing in Jesus because of the history of the church–which you have to admitt got way away from Jesus quite a bit of the time, ie. the Inquistions, Crusades, seculariztion of the church, continual splitting of the church sometimes over minor points and sometimes not (bah humbug on Calvanism) but all they see is the splits, they are not interested in the theology.
Some other people have been badly hurt by people professing to be Christians, hurt as children and there isn’t much one can say to heal that in this life. Others seem to be rebelling against Christianity as part of rebelling agains their parents. And others simply don’t believe in the reality of God.
I also agree, God is quite capable of putting truths that can lead to Him in other religions, some people may even come to meet Jesus without knowing it if He wishes it.
For these people, once they actually see Jesus I think belief and repentance will be almost instantaneous—and I don’t see a time limit on salvation. They will finally have all the data they need for a decision as various things in this life have kept them from having the tool/gift of faith. So I think they will be with Jesus and us pretty quickly. This would also include most of the people who never heard about Jesus.
For others that have deliberately chosen evil, and I am not naive enough to think that some people have not made that choice I don’t know how God will get them to come to repentance—but I believe He will and I am quite happy to leave it to Him. But until they have repented I don’t think they will be with those that already have—unless there is a place where even then we do witnessing and testify about Jesus.