I don't mean to challenge the quality of your experience with it, but out of curiosity, what's wrong with wpa_gui? I mean, while I haven't been using it lately, preferring some simple scripts to notify me about thr network status, I used it on Linux too. It's the only graphical frontend to wpa_supplicant which I'm aware of, and, in spite of its ugly interface, it seemed to do its job fairly well.
The PC-BSD network manager was a really good one (included in the sysutils/pcbsd-utils port), a pity it had to be discontinued, as I feel its kiss qt5-based interface would have got along well with the NetBSD's overall spirit.