When Great Grandmster James Mitose awarded Bruce Juchnik with
Menkyo Kaiden (full mastery of the MA) and Inka Shomei (spiritual authority/approval in zen buddhism), in Late 1979, arguably, Juchnik had the power to choose his title and organize the system as he saw/sees fit.
With this certification from Mitose, Juchnik could have declared himself the Soke of Kosho Ryu upon Mitose's demise but chose not to. Rather, the original intent was to have Thomas Mitose study with Bruce and assume the role of Great Grandmaster, hence why Bruce chose the Hanshi (root master) title instead. Unfortunately, Tom only studied with Bruce for a short time and decided to go on his own. I think Bruce is still hopeful that Tom would return to complete his training.
When choosing a grading system Juchnik Hanshi chose the more conventional modern Kyu/Dan system rather than the older Shoden, Chuden, & Okuden. My guess is that the modern system was chosen because the system is now primarily taught in the US and that Mitose Himself used a Kyu/Dan grading system. The higest grade chosen was 7th Dan as Juchnik made honorary titles (Shihan, Kyoshi, Renshi, Hanshi) seperate from martial rank.
In Kosho Shorei Ryu, the title of Hanshi is also given to any of Mitose's original Black Belts who get involved in the Kai. Such as Thomas Young Hanshi & Paul Yamaguchi Hanshi.
I hope this helps.
_Don Flatt