Not that I don't think a 1.5" trackball wouldn't suck for games... (it might, it might not...) but when I was at Borders the other day, they have the assanine counterintuitive, barely helpful "Title Sleuths" kiosks with a keyboard and a tiny trackball... and that sucker spun very well FWIW. Of course for some games it's not the spin, so much as the real estate travel for manuvering...
*shrug* it won't feel the same, but maybe with appropriate settings the playability won't be horrible. sounds like you'll be the guinea pig if you go forward with it -- let us know how it works out.
rampy