Thanks very much for the reply. We had talked at one point about possibly using the classes on the navigation tab, but are aiming for an automatic solution that doesn't require staff to manually update those.
If I did clone the css list web part to make a custom one, where is the code that actually generates the code for the menu? I'm looking at the code under CMSWebParts > Navigation > cmslistmenu.ascx.cs, and it only seems to be setting up the properties and not outputting anything. This feels like a dumb question, but we're usually focused mainly on creating our own custom user controls and web parts, so I'm not terribly familiar with trying to clone from and modify existing ones.