"I thought I knew what the BSD license meant, but my understanding of it hadn't considered the implications for hardware distribution, and I imagine that's true for most people."
Right, and no offense, but your solution was then to just solve this specific problem rather than ask about what other legal implications you were missing.
For example, ISC specifically only mentions "this software".
If you were to ISC license everything, but also include say, IC layouts, they arguably would not be covered.
Worse, IC layouts ("mask works") are, in the US, a completely separate set of rights that are arguably not covered at all by the "use, copy, modify, and distribute" part of ISC (and have the software issue).
Basically, there are a large set of issues with current licenses and open hardware, and you identified one, and then immediately switched to some other license without considering the other implications as well. It may well turn out for your particular project there are no other interesting implications, but as you say "Details like these are easy to gloss over, but they can have a major impact on whether open-source projects can actually be used by others."
With no offense meant (really), I don't think what you've demonstrated is a good example of handling that well.