So I'm trying to mod the TZ to get closer to that. Whatever it takes. 1 meg pot, magnet swap, etc. The P90 TZ actually uses ceramic magnets to get the same sound of the regular TZ that has Alnico magnets. I think all I need is a bit more treble out of the TZ in the neck. Also the P90 TZ is 16.77K, so pretty hot.
If memory serves me, the P90 sized TZ has a double thick ceramic magnet. Its two rows of screw poles are directly in contact with it.
I wouldn't expect another magnet to make it work in neck position. Any AlNi(Co) bar should just make it less focused and darker by weakening its magnetic field and increasing its inductance (which is already high: my archives state that 7.77H have been measured here on this exact model. With a normally sized A5 bar, it rised to 8.88H according to my notes. It's 1/4 to 1/3 more than for a regular P90, for the record).
1M pots would make more peaky the main resonant peak, without cancelling the rather heavy comb filtering effect that Dual-Resonance creates beyond this main resonant frequency for this model. It would potentially make the sound heavy in the hi-mids but still with dark harmonics.
If I had to make it work in neck position, maybe I'd try to pull off 6 screw poles: the 3 ones closest to the bridge under the wound strings, the 3 ones closest to the neck for the high strings.
You migth appreciate the contrary. Or find interesting to pull off the screw poles in the whole same coil of your choice. Or pull off 3 screws only in a coil under the bass strings... Experiment.
It should lower the inductance and weaken the magnetic flux, making the pickup weaker / brighter while keeping it in humbucking mode.
A more radical solution would be to wire the P90 TZ in parallel. It would give the brightest weakest tone this model is able to achieve by itself (by dividing by 4 its overall inductance in series and cancelling the comb filtering due to Dual-Resonance, this time).
You might also put a 10nF capacitor in series with the neck PU. Just be aware that it would change the behavior of any tone control after it and would alter the response when both pickups are enabled.
All of this boring post is based on past experiments with the model mentioned, FWIW. Now, do what you want and be happy.
EDIT - Below a screenshot about the DiMarzio P90 TZ with all vs half of its screw poles (I had forgotten I had that in my archives, currently way more crowded than my old brain).
it shows the electrically induced resonant peaks of the whole PU in series, with standard pots and 10' cable. Dotted lines = phase response. Bottom ragged lines = THD. The test had been done in such a way that it wouldn't show the effects of Dual-Resonance (which can be seen when each coil is excited separately in humbucking mode. Here both coils were excited in the same time by a perpendicular ultra-low impedance air coil).
The version with half screw poles is shown by the red line (and tighter, as expected)...
With the pickup wired in parallel, the resonant peak would be higher pitched, changing the balance between fundamental notes and harmonics for a single coilish tone.
