I have a non-Alembic fretless with an extended thumb rest.
different strokes for different folks. you've got an intersting bass there, sir. my essence fretless is a 5-er, i just did a rough measurement of the string displacement from center when i goose the B-string and i get aboot 3/8". that would be pretty close to hitting the thumb rest on the reverb bass. while playing, i either plant my thumb on the neck pickup or on the neck uparound the 14th position. or on the B-string itself. that thumb rest would be the first thing to go if i bought it. which i won't.
Plus the non-factory toggle switch
yeah, i missed that first time around. looks like some home lutherie gone bad. kinda gives ya a preview of what you'll find in control cavity should you be foolish enough to venture within. $4400 USD? good luck to all!