"Why... ???"
As far as sacrificing body shape for a 24 fret neck, yes. Unless you do not want to use the extra four frets (extra compared to the original Fender), you will have to cutaway deeper on the treble side to allow access to the extra frets. So the body shape will change.
As far as sacrificing pickup positions for a 24 fret neck, no, not necessarily. You can fit a P pup or a J neck pup in its usual position. But you will have a comparatively small space between pup and fretboard for popping strings.
The 24th fret lies 25.5" from the nut. Here are standard pup positions (centerlines of the pickup coils shown).
