Find me one art completely different from previous arts
Exactly, there are only so many ways that the body can move to punch,kick, etc effectively. ALL arts were new at one time, and it is only through sharing it with others on whether or not it has stood the test of time or not.
What is going to seperate arts is through their strategy and approach to combat.
For example, if you think that the legs are the most effective body weapon you are going to use and find ways to implement kicks. If you are basing it on kicks your distance and approach to that will be dictated on that was well, meaning you are going to find a distance to use those kicks. Now most would agree that ONLY relying on kicks has it's drawbacks, so along with using the kicks the founder would learn techs and concepts that allow other body weapons to be brought into play to support the use of the kicks.
Now, you have someone else who thinks that punching is the most effective method and bases his strategy and approach on using the arms.
Then along comes a 3rd person, he studies under both of these men. He doesn't think that either approach by itself has all the answers so he starts out to combine them. But what techniques does he use? If he just teaches both arts as a whole then there is no new art. BUT, if he looks at the methods of each seperate art and takes some from each and builds the use of kicking/punching methods so that they fit together into a different approach than it is a new art.
To illustrate what I mean. Let's say that through his experience he finds that fast, whipping punches are better and that to control an opponent he should remain medium distance or closer. Would it be smart to then use lots of high kicks to the head? Probably not, he is going to rely on low level kicks that are probably snapping as well to keep the opponent in closer.
Now whatever techniques he does choose, they should share a very similiar method of execution (body mechanics) so that you only have to learn one way to move and everything builds on that foundation and all the parts fit into the whole.
We can now do that with everything in every martial art. punching, kicking, joint locks, throws, etc. You are going to find LOTS and LOTS of different combinations that work (and many that don't). So to say that only the masters back in Japan/Okinawa/Korea had the answers is ridiculous.
This does not even touch the subject of an arts philosophy to life either. Does your art apply it's concepts on more than a physical level? Or is it a seperate thing that is added to the physical part and taught along side of it?
Find me one art completely different from previous arts
You aren't going to find that in ANY art in Martial arts. As much as I hate to quote Bruce Lee (and I paraphrase) until someone comes along with more than 2 arms and 2 legs....
4. All these "new," arts--and there sure are a LOT of 'em, aren't there?--are really just reflections of what somebody's found out about their own training. Or they are marketing strategies.
Again, ALL arts are someone's personal expression of what they found worked for them. I agree with the marketing concepts part, anything "more effective than ever before" or "deadlier than any other art" stuff is marketing.
The thing that always interests me is about the fact that people bring up duping people out of their money by having a crappy product. I agree with this statement, but again this is something that goes across the board in MA's. Everyone can probably think of a school in their home town that is a "legitimate" style but is a very crappy school with poor training methods. Of course in the old days they would have had a challenge match to prove that their style had merit and many new styles would not have passed that test.