Historical Masters

This has been harder to formulate an answer to than I thought it would.

As a Shorin-Ryu Practitioner my answer would be Higa Yuchoku Hanshi. As the teacher of Aragaki Sensei, with whom I began studying Shorin-Ryu and who was the instructor of my current Sensei, it would be a fascinating way to return to the source. I did initially think Chibana Chosin, but Higa Hanshi's path to studying with Chibana Chosin, was not straightforward. He did not begin training with Chibana until 1948, which was 20 years into his karate training. Prior to that he studied with Shinzato Jinnan, Miyagi Chojun's Protégé, and with Miyagi himself. He also trained with Miyahira Seiei whom is credited for our unorthodox Seisan which is like Matsumura Seisan but follows a distinct embusen and shows influences from Naha Seisan. It would be fascinating to see what changed between Higa Hanshi and Aragaki Sensei, and also to have a chance to ask where some of the kata we practice come from as they are not part of the Kobayashi-Ryu core kata. 

As a martial artist, I think I would have to choose Matsumura Sōkon. He is an unavoidable "choke point" in terms of lineages, as he instructed teachers from whom much of modern karate comes. He had an undeniable influence on Shuri Te through his instruction of Ichiji Ankō, Yabu Kentsū, and Hanagusuku Chomu. And Tomari Te through his teaching of Kyan Chōtoku and Motobu Chōki. All of who in turn had influences on the founders of Modern Karate. Training with him would potentially solve a big part of my Seisan Research Puzzle, and possibly clarify the origins of other Kata he is reported to have taught. But, as a martial artist, he is credited as a peerless warrior in his generation, and his reputation over shadows others in that field. For learning the historic fighting skills of Te I cannot think of a better candidate. 

As an amateur Karate History Enthusiast, I would have to choose the mysterious Ryū Ryū Ko. Essentially, he is the biggest mystery in Karate history. Credited as the teacher of Arakaki Seishō, Higashionna Kanryō, Kojo Taitei, and Nakaima Norisato his alleged influence is not inconsiderable when compared to even Matsumura Sōkon. Indeed, he apparently taught a system potentially related to the systems that birthed Kingai-Ryū and Uechi-Ryū. However, considering how different all the systems he apparently influenced have become in the modern era, and indeed, how dubious some of the claims of training with him become under scrutiny, training with him would answer two questions: Did he actually exist and is not some form of cryptid, and what of his actual system survived into modern karate. 

Edited June 20Jun 20 by Wado Heretic