Well, it's only a 4 string 20 fret fingerboard and I hardly if ever play above the 14 fret, not because I can't but because it really isn't something that is needed for 99% of the music I play. (Blues, Jazz, ect.) Most bass players that do a lot of chording and solo work more often than not play a 6 string bass. Having said that and after some more thought I don't think I have to start my drop off at the 14 fret, the 16th or even the 18th fret may be best. After a level, crown and polish from the 16th or 18th fret to the nut and even if I end up with a differance of .005 - .008 lower in height at the end of the fretboard I'm thinking it would be a benefit to me for getting my action were I like it. I doubt I would ever be able to feel the difference since trying to play a bass line on the 18th fret on the E string let alone the G on a Fender style body just does not make sense and is hardly if ever called for. I guess the reason I even thought of throwing this out there is to see if there is a reason not to do it that I'm not thinking about like not being able to tune or intonate the bass, or It would look unsightly, or not being able to level the rest of the frets down to the nut.
And I'm not thinking of mixing up the fret size's or having lower in height frets at the 14th through the 16th and then going to higher frets again to the end of the fretboard, just a slight drop off on the last few is all and since the width's on the fret wire's are almost the same I doubt someone could see the difference without a close inspection.
I really do appreciate your's and any (and all) input also since I want to give enough time in this thread for somone to let me know if there is really some fundamental reason why it should not be done. It's an idea that I won't just jump into.