Nope, sorry, no chance on bolt on.
On any given instrument body, with 20 frets or 24 or any other number, the neck length does not change as long as you stay with the same scale length and bridge position; what changes is the length of the fretboard, not the neck.
We can do a Stanley in a set neck model if you'd like, that would be the closest feel you can get to a bolt on by playing an Alembic; I think you will find that the punchiness & attack of an Alembic, be it set neck or neck through, can withstand pretty much any comparison.
Many of our club members are owners of bolt on basses from other manufacturers, besides their beloved Alembics, and I'm sure they 'd be willing to share their impressions of the difference between Alembics and bolt on basses.
I don't know if you have tried any Alembics yet. If you have, please let me know what models you played, what your impressions were and so on; that way we can assist you better. If you haven't played one yet, we encourage you to do so; you can find a list of our dealers here :
http://www.alembic.com/family/usa_dealers.html Valentino