Re: Humbucker with single coil dynamic
Dynamics aren't determined by pickup alone, a high output pickup into a high headroom amp can be more dynamic than a low output one into same amp. It's the interaction of output, distortion and compression/limiting.
That said, if you want more mids, almost anything has at least more relative mids than a polished A5 magnet, which is the most common magnet...
I have a JB with an A3 magnet, it has a high end sparkle that isn't there with A5 with those coils, and is low output with more even midrange. Rather squishy feel, but a lot more dynamic than stock. I actually use it as a neck pickup... That's an extreme oddball configuration. [Also is installed stud poles towards neck, with side under wound strings cranked way down, 3 0.75 hex screws swapped in under wound strings and screw poles adjusted to even out string balance (WAY up on low strings).]
Same guitar has a PATB-1b, which is a high output bridge pickup with soft attack and ridiculous response to pick articulation. Parallel Axis pickups tend to be very dynamic (though sometimes dynamics are expressed curiously, like in the face-melting high output PATB-2 Parallel Axis Distortion, where they show up as tone changes more than output).
But if you are looking for humbuckers that feel more single-coily, '59/Custom hybrid is one to look at.
If the dynamics you are looking for are lower output, with a bit more squish in the pickup, rather than harder attack, UOA5, A2, or A3 magnets might get you closer, too. Roughcast A5 is like a polished A5, with slightly less high end, and maybe some mild changes to EQ elsewhere. About same output as polished A5.
A3 is a fair drop in output, lowest output and least bass of any magnet I've tried. It's sort of like an A2 with lower output, less bass and more treble, but the treble is smooth in almost any pickup I've heard with it, rather than harsh.
If you have the skills and patience to swap magnets yourself, it's really worth trying them all to see what you like. Cheaper than swapping pickups, certainly, as long as you are careful not to damage the wires where they connect to the bobbins. Though with unique pickups, what you learn about magnets may not apply to other pickups quite as predictably, you'll still have the extra magnets to try in any other humbuckers that aren't quite to your taste.
Last, if you really want single coil tones AND no hum, best option for most players is something like Seymour Duncan's Stack Plus line (I like STK-S6/STK-S4m/STK-S4 or STK-S6/STK-S4m/STK-S7, but I'm a Gilmour/SRV fan who likes light strings and doesn't get along with hum/noise at all), or Kinman pickups.