It's taken me a bit to get back to work on this, but I've looked through what I have and here's where I stand on research thus far...
Rokkomann....everybody pretty much agrees they were a distributor...BUT there is an example of a an electric guitar made in the 1970's period with the name "Rokkomann" on it. It makes me think they either had this made for themselves as a 'brand' or they dipped into actual production during the red-hot 1970's electric guitar craze. Interesting if they did. Rokkomann clearly bought the Maya trademark in January of 1976. One wonders if they indeed had the name trademarked prior to that date, since Maya guitars were clearly in existence prior to 1976.
Tahara...according to Saga Musical Instruments, who bought Tahara, the company made mandolins and acoustic guitars in the 1970's with the "Maya" badge...zero El Maya guitars according to sources at Saga, although they're often credited with making both badges. Tahara was located in Matsumoto, Japan, not Kobe, which is interesting...and Saga didn't buy them out until the mid to late 1970's.
Maya Musical Instruments....I can find no evidence for this company's founding, although it's stated universally that the company was located in Kobe (as was Rokkomann) and was destroyed in an earthquake in 1995-96. It's suggested the company took their name from Mount Maya which is near the city of Kobe, Japan. It company existed because we have labels inside Maya and El Maya guitars with their name. Perhaps Rokkomann owned Maya directly...I don't know. I'm unaware of any other guitar badges made by Maya, although that lies in the realm of the possible.
Chushin...I'm convinced that Chushin was responsible for some El Maya badged guitars made in the 1970's because of the high quality they demonstrate. El Maya guitars were made well after 1980 and are still prized by collectors, although they were not high sellers when they were available new. I also believe Chushin was responsible for some Maya electrics as a lower-end alternative to the El Maya high end guitars made back then. Chushin was often utilized by high-volume makers like Charvel and Jackson, so it's reasonable that Rokkomann would select them to produce both badges for the world market. Chushin is still in existence so we might be able to get an answer from someone about when they made the badge in their factory. There's evidence Chushin may have been a member of the Matsumoto Musical Instruments Association which was where Tahara was located, so perhaps Maya and El Maya were products from the Association. It may be that Rokkomann approached the association at first to produce the badges until it dissolved, we just don't know yet.
Props to Memag and others who contributed so heavily to the first discussion on these guitars!