It’s been one of my little tone quests to fine a humbucker which has a truly good single coil sound when split. An Idea I had recently though was to combine a true single and a single coil-sized humbucker in one, so that instead of a splitting a humbucker, you’re simply switching between two different pickups in one enclosure. These could have a nickel cover for more of a classic look.
You could even have the single coils as hum cancelling single coils, so that in both modes there is no hum, another problem with conventional coil splitting. I saw this working with something like a Seymour Duncan STK-4 and Lil’ 59, or a Dimarzio Area 67 and Pro Track. Dimarzio did something similar to this with their discontiuned “multibucker” pickups, but that was more like two different humbuckers in one, and the Dimarzio Area series have progressed how good a hum cancelling single coil can sound since then.
I’ve submitted this as an idea to Seymour Duncan’s SDRL:
As do Warman guitars with their G Rail: