Business class on Southwest is not what you'd call business class elsewhere. You do not actually get a larger seat. You get priority boarding, a free drink, and maybe another goodie or two. Airtran does have "business class" with domestic first-class type seats, but the upgrade costs is significant.
For some reason, I think that Southwest points convert to "Wanna Get Away" fares at something like $0.016, so that's better than booking using UR points.
You didn't even say where you were flying from, so it's difficult for anyone to be much help with schedules and fares. Depending where you are going, getting home by noon-1PM could be easy or impossible.
Why don't you post where you are traveling from and what you see for fares? It's also possible that you might get a better deal by, say, converting UR points to United or to BA and flying on American, depending on your origin. Not at all definite, but possible.