Wouter; welcome to the group. I like your idea of a Series I with a maple and ebony neck, mahogany core and coco bolo front and back; the combination of those woods with Series I electronics should produce wonderful tone. I would love to have such a bass!
Barts are great pickups; however, your idea of putting Barts in an Alembic doesn't seem appropriate. I believe it to be the case that Alembic electronics are designed in tandem with their pickups; the pickups and electronics work together as a unit. I would imagine that most of the members of this group would suggest that replacing the Alembic pickups with Barts would not result in improved sound. Admittedly though, I've never tried it and perhaps you have, so you may know more about that than I. But for all their amazing wood work, the starting point for an Alembic is the pickups and electronics; an Alembic with Barts just wouldn't be an Alembic.
I do not recall having seen an Alembic bass with a three band EQ; they may have custom made such an arrangement but it certainly isn't a standard setup or one of the many modified setups I've seen. (Of course I must admit to an unreliable memory, for all I know I may have seen such an EQ yesterday .) Generally, the tone control on an Alembic is the low-pass filter. And generally, the filter is augmented with a Q switch. Additional enhancements are bass and treble boost/cut switches. And then there are the bass and treble controls as found on Epics, Excels and Orions. I suppose Alembic could custom make a three band EQ, but you are probably talking about some bench time and its corresponding cost per hour.
Perhaps the standard Epic controls would give you a setup similar to what you were requesting.
