I agree that the Alembic Series electronics do provide a lot more control over "mixing" the humcanceller with the pickups, individually.
Regarding KR's original question - I haven't worked with humcancellers (aka "dummy coils") on my own before, but my understanding is that yes, it CAN be as simple as just wiring up a dummy coil in series with the pickup. The windings in the dummy coil should ideally be the same characteristics as the pickup (e.g. # of winds, resistance, impedance), but wound in reverse (or just swap the leads) and of course omit the magnet(s). It also needs to point the same direction as the pickup.
People have modded Strats like this as a simple mod, and Strats don't have any of the complex active circuitry of Series instruments, so yes it does work - here's an example with a wiring diagram, and some explanation:
https://www.frettech.com/frettech/dummy/index.html#:~:text=connect%20the%20leads%20coming%20out,dummy%20coils%20are%20directionally%20sensitive.
I have seen some other instruments with simple dummy coils like this as well.
But as Songdog noted, it gets a bit more complicated if you're trying to use it when multiple pickups are selected, especially when there are also active electronics that allow the gain to be set individually for each pickup - like on a Series instrument. I assume that is the reason why the circuitry for the humcanceller on Series instruments is much more complex.
If you're just pairing a single pickup with a dummy coil, though, I believe it should work as long as the dummy coil meets the criteria above.
Side note, as the article I linked above points out, there will almost certainly be some minor treble loss, even if you match the characteristics perfectly. I recall reading an article that explained the full theory behind dummy coils / humcancellers, and it explained that it is literally impossible to avoid at least a tiny amount of impact to the tone. But if it's designed well, it may be so little that you realistically won't notice it. And it can be significantly better than if you replaced it with a humbucker.