Since you have three on the humbucker, I'd be tempted to a coil cut with one. Filtertrons a bit of a different animal, but with most humbuckers you get a bit more sparkle from the single coil setting. The other setting I would consider (taking a page from the Esquires) is to take the tone pot out of the circuit and use a cap to get a tone setting you like. I don't have a bass set up that way, but I can see doing it. There's usually one tone setting that I use for pretty much everything, although I occasionally want to dial in something different. So having a setting for "that one setting", having another for the tone pot full range, and having a coil split might be nice, without getting over complicated. Just a thought...now going to take a look at Weirdbit's idea ;-)