BYU's program is very good. But if you go there as an undergrad, you're still learning from many of the same faculty.

It's not a terrible idea to go to the same place to get your MBA, but there are those who believe it's best not to. On the other hand, you'll never find anyone who believes you SHOULD get both degrees from the same place unless that place is Harvard.

Coming from UVU won't be a problem (BYU accepts UVU students all the time). But you'll really want to focus on that GMAT score and have a reasonably good salary before you apply given your employment tenure. Those are two measures that get evaluated in rankings