As much as these make sense aesthetically and ergonomically, that would make them just about impossible to replace with anything else when the tone doesn't suit the user. Using regular soapbar pickups makes much more sense because the pickups are easily interchangeable - since many soapbar sizes are standardised and used by several manufacturers.
That said, there are some manufacturers who give their soapbars a little notch for your thumb (Yamaha did this on some RBX models, and Ibanez on the SRX series pickups, and Delano does it on those weird oval pickups of theirs) and then there's Dingwall who give the ends of their soapbars a curve so there's always a small area pointing "up". None of these use standard sizes.