I absolutely agree: about the
beauty of that bass, and that it would look better IMO as well with less than the "Spector Standard" of 24 frets - I'd stop at the 22nd after the last Crown Inlay as a) I think the 22nd wouild still be playable using "standard technique" and b) a blank space between the last Inlay and the end of the fretboard would look nice to my eyes.
However, I realize that it would involve a good amount of material, time & CNC changes to produce 22-fret neck-through blanks for only
one USA model and hardly be cost-efficient. So a pass on that from me.
If I can make a suggestion, you might want to try a 40
P5 (the 5-string version of the soapbar-mounted EMG "P") / 40DC setup before going to the "standard" P/J pickup arrangement. I put that into a "spare" ReBop 5 DLX FM I had (It was my 1st Spector so there's sentimental value, plus I'd never get what it's worth on the Used Market right now so why not mod it and put it to use?) as a "Testbed" to emulate
Fender's pre-2008 American Deluxe Precision V, the only P-Bass I've liked the tone of. The 40P5/40DC gives you 97% of the "classic" EMG P tone (the 5-string version is "reversed" with the E & A coils behind the D & G, slightly tightening and loosening the former and latter... but the vast majority of 4-string P/J Spectors have Reversed Ps as well) and dialing in the Dual Coil gives you more-than-a-bit more "growl" than a solitary single-coil "J" does. I'm not sure what EMG's Return Policy is, but if worst comes to worse you could always sell the 40DC and put that towards a 40J. I simply think it's a more interesting sound than the ubiquitous P/J tone.