This isn't the exact question you've asked, but it's an idea of mine.
People always have to seperate their 360 and 270 degree driving wheels - one uses a spinner-like mechanism, one uses a POT and self-centers. But then you notice that 270 degree games play fine with a spinner, just no limiting and no self-center.
It may be easier to add 2 360 and 1 270 wheel, but you could really make a wheel that uses a spinner mechanism and has limiting pins that slide in and out of the way, and a self-centering spring that can be unhooked.
It's harder to make and you may not like the idea of unhooking things to switch modes. Just an idea.