I disagree.
Unless you can jet around in your private airplane, there is no way to try out every bass by every builder. Even if some shops carry a lot of high end boutique basses, I'm sure you can't even try out one full production line from _one_ builder in one shop.
I even think you can not know every boutique builder out there, I virtually come across a new builder once a week via talk bass or other parts of the internert (my newest discovery, Laurus Basses, )
Now if you can't know every possibility out there, let alone play it, you can't know if amongst it is _your_ dream bass.
Also, I think if you have 2 basses built to 100% identical specs, they will sound different, the better the builder the smaller the difference, but I think it will be there.
With all that said, I see nothing funny or wrong in collecting ideas and inspiration for your "dream"build, after all, it's a bass, it doesn't have to remain your "dream" instrument until the end of time.