According to the statement about the Badger air-opaque colors:
"They are suitable for use on illustration board, photo materials, acetate, and all papers. " They are entirely water-based in an acrylic copolymer. Sounds like the Badger paint is not much more than an acrylic watercolor--not good for models. In addition, the Games Workshop Acrylics also sound a bit like watercolors. It appears that by spraying one onto another, you are essentially re-constituting the paint into its original liquid form. According to one website, the Games Workshop acrylics have been successfully used as an undercoat on figures prior to spraying on an enamel topcoat--but then organic solvents shouldn't attack water-soluble pigments.
You didn't specify what you are working on, but I would submit that using acrylics designed for modeling (Testors, Gunze, Tamiya, etc.) should be used exclusively for that purpose, or at least just use one manufacturer's paints for a project.
I'm not sure, but it appears that Mr. Topcoat may be a lacquer. Since lacquers, like enamels, aren't water soluble, it's very possible that Mr. Topcoat could be used successfully over acrylics, provided they've had sufficient drying time; however, I would shoot some test panels before trying it on your pride and joy. To draw a comparison, I've used Testor's Dullcote (a lacquer) successfully over Tamiya acrylics.
Hope this helps.
Gip Winecoff