Thanks for all the good insight and discussion. By January I'll have a small hole burning in my pocket and I'm looking at a few viable options.
a) send bass to Lakland and have them install the new lined-fretless neck.
b) trade that bass (a 55-01) on the significantly better-preamped 55-02 fretless, so I don't have an extra neck just laying around.
c) ebay
d) buy parts from Carvin or Warmoth and assemble my own, to my liking.
Jimmy, I think your advice to go for as much visual aid as possible is an excellent idea. I totally get where James (malthumb) is coming from, but I often play in situations where good reference pitch is hard to find (9-piece horn band, for instance).
The irony of ironies is that there's a nice Series fretless on ebay right now. I can't afford it though, and if there is a next Alembic for me it will have a smaller, lighter body..
I figured I could unload a few instruments to generate some capital, but my 14-year-old bassist-son won't hear of it.
I am reminded just how fortunate I am to have this sort of dilemma. I have plenty of gigs, a decent job, loving family, good health and friends.
John