To change the scale of a thru or set neck instrument, you would have to remove the fretboard without wrecking the neck, and replace it with a new one. This is a difficult-to-impossible task. With an old instrument, you could steam it apart, but modern adhesives are much more resistant. Or sand it off. Either way, hard to imagine anyone would touch the job.
If you managed to do the first step without completely destroying the instrument, you would then have to move the bridge about 2 inches, assuming there is enough room. This would have the same effect as radically moving the pickups - it would change the tone of the instrument.
If your goal was to have your old guitar but with a new scale, it won't work. It might as well be a new guitar. And if it was a valuable instrument, it won't be any more. If you don't like it the way it is, sell it and get something else.
With a bolt-on, installing a conversion neck would also effectively move the pickups, but only slightly.