Got to agree with Mike here. You're probably looking at $1K or so to buy a replacement set of electronics, but check with Alembic directly on this if you have an idea of what you want.
Almost universally, asking Alembic to do after-the-fact upgrades is prohibitively expensive and doing it yourself can have a negative impact on value. Anyone who puts non-Alembic electronics into an Alembic instrument will find the market shrink and the resale value can plummet severely.
Of course, there aren't thousands of them out there in every possible configuration waiting to be bought, and buying and modifying this bass will be cheaper than ordering a new one from scratch. You just better be sure it's what you want to own before you jump into any mods.
It's a great buy, and if it had Europa Electronics, it could be $300-500 more in market value.