I guess I'm going to be the odd one out here. I'd go with W&M or USC and then JMU.
My DC also had similar options including the spring admit for W&M and Honors College at JMU. I was hoping my DC would consider the W&M spring admit, but like your son, they weren't interested. I know students who have gone that path and it has turned out really well. Often those kids grow (mature) more than the kids who entered directly in the fall. It seems like there is a lot of switching around of friend groups that first semester/year, so I don't think the spring admits miss out on that much. And, they will have a strong cohort from their trip abroad. If you have Facebook, you can join the W&M Parents page and ask parents about their experience. I've heard very positive things. If your son could also check out the Instagram page for the Verto group:
https://www.instagram.com/vertoeducation.
I also know several NoVA kids at USC who are very happy. We really liked the JMU Honors College but my DC wanted a change of pace from NoVA and wanted to be further away. I wouldn't worry too much about the politics of UofSC. Most college campuses and cities are going to be pretty liberal. South Carolina would be a fun place to visit too!