There may be some LDS who fit into that cateogory, just as there are some Methodists and Presbyterians and Orthodox who would fit into that category; not by virtue of their membership in any organization run by men, but by virtue of Christ's having written their names in the Book of Life.
The LDS Church is not a true Church as they do not believe in the Christ revealed in Scripture. Nevertheless if God can make Sons of Abraham from stones, then he can make Children of God from Mormons.
When his disciples heard it, they were exceedingly amazed, saying, Who then can be saved? But Jesus beheld them, and said unto them, With men this is impossible; but with God all things are possible.
(Matthew 19:25-26 KJV)
But then it's not enough to "just believe." It's a simplistic slogan. Now you are forced to qualify it.
You are presenting the deceptive "we are all a little right" theology that says no church is God's true church, or, worse, all churches are God's true church; everyone is right a little bit.
God would never teach us such a lie.
But Jesus beheld them, and said unto them, With men this is impossible; but with God all things are possible
Yes it is, it's always possible that even the worst sinner will repent, and that the worst apostate would come back to the catholic and apostolic Church and embrace its orthodox faith.
But you are appealing to your own interpretation of Scripture. They could just appeal to their interpretation of Scripture and say the same thing right back to you.
-A8
I'm glad that God (and not man) decides whose names are written in the Lamb's Book of Life.
Whew...