Agree with a lot of what @Muzz said here. I've not been playing bass for as long as many here but I'd tried enough basses over the last five years or so to spec out what was most comfortable for me, i.e. target weight, neck profile etc. for my custom build. I did also go to the workshop before ordering and looked at a few of his basses and necks before committing to the project.
I probably played it safe on a few items like tone wood as I went for Alder as opposed to anything more exotic. but light weight tuners, 40mm neck width etc. we're all musts.
I wanted active so I went for a Nordstrand Pre, mainly because it is inspired by the Sadowsky pre but an East would have been equally good. Jon Shuker also set me up with a solderless pickup system so I could replace pickups easily if I wanted to try different ones.
that isn't to say I didn't get a few things wrong. The drop top I originally had I ended up not liking. This for me was the hardest part of the custom build - trying to visualise a slab of wood into a finished guitar top was really hard. I went into the build wanting flamed maple then spent months changing my mind and ended up with something I didn't like. I've now sent the bass back to Jon to have the drop top redone as flamed maple, a costly mistake caused by me allowing myself to get too caught up with exotic woods etc.
however, it was an amazing experience and despite the asthetics I ended up with a bass I love playing. Like @Muzz my Shuker was my go to bass and I'm really missing it at the moment (hence why I bought the ACG).