If anything Kinnikuman copied DBZ! Even though they're both almost completely irrelevant in almost every way... Besides.. I don't believe there was any Maelstrom in Kinnikuman(1st). The power level system is very commonly used. And what are you smokin?! "Warriors"... Since when did suguru or mantaro have they're own "warriors". And you must be some effed up if you think kaio-ken has anything to do with "ultimate muscle".
Well, if anything, you should visit
http://www.kinnikuman.jp. Yes, you are reading it right, it says 25th ANNIVERSARY.
Then, you should take a look at this:
Who is that guy in the left?
Probably you are asking yourself: What is he doing in Toriyama´s first big shot manga? (Dr. Slump). Toriyama is/was a fan of Kinnikuman? How big was the manga back then? (1979-1980).
I know there are older fighting shonens, like Kurenai Sanshiro, Tiger Mask (one of the main inspirations), the Ultra Family (the other inspiration), A s h i t a No Joe and Kick no Oni, but none of them had a galactic/chojin/superhero/wrestling/tournament/good vs evil (seigi vs akuma) setting.
Of course Suguru and Mantaro are warriors, literally. Blame the UM dub if you never heard that. And about the Kaio-Ken example, i cited it because it works in the very same way that Suguru´s Fire Spirit.
Even when I havent watched Kinnikuman Nisei that far (you know, the japanese version is behind the american), storywise, nothing can defeat the Kinniku family Fire Spirit in a power match, but there are abilities that can nullify the effect...
You guys should have this series in higher shrine. After all, this is a Kinnikuman forum, right?