I think this is a great effort, and if you'll recall Google went and attempted to do the same thing with VP8, but found that people could file patents faster than they could release code. I would certainly support a 'restraint of trade' argument, and a novelty argument which implies (although I know its impossible to currently litigate this way) that if someone else (skilled in the art) could come up with the same answer (invention) given the requirements, then the idea isn't really novel, it is simply "how someone skilled in the art would do it." I've watched as the courts stayed away from that theory, probably because it could easily be abused.
 Conspiracy theory or not, the MPEG-LA guys kept popping up additional patent threats once the VP8 code was released.
Anyway, I'm not a lawyer, and none of this is legal advice or patent advice. Just my thoughts (or perhaps frustrations) on how hard it is to generate deliberately patent free technology. That difficulty suggests to me a way in which patent law could be improved.
But you don't need an expert for novelty. Either you can show a prior art or you can't. I'll grant that there may be some some edge cases where the prior art needs some nuanced interpretation from an expert witness.
Lets say someone asks you to make a mud pie and put bits of lavastone in it. You make your mud pie and then you patent "system and method for creating a mud pie with lava stones."
Perhaps there is no prior art because nobody asked for a mud pie with lava stones, perhaps there is no prior art because others who made mud pies with lava stones didn't see anything useful about it. But someone, somewhere, filed a patent. And the patent office grants it.
The question I pose is how to come up with a defense that anyone skilled in the art of making a mud pie, would make one with lava stones in just that way ? And yes, I know all the legal arguments why it doesn't work like that, so my point is how do we fix the patent system such that utility patents on methods or combinations of methods, would likely be independently arrived at by anyone skillled in the art?
How do we fix it so that Cisco, writing their patent free video codec in the open, doesn't get "scooped" by someone taking their project, projecting out a month or a year in advance of what it is going to need to work, and then throwing together a provisional that pre-dates the open source project getting there, thus depriving the people working on Cisco's efforts their ability to ship without hindrance?
 Really, just dirt and water.
This is begging the question (in the original sense of the phrase). The process is usually not somebody saying "make me a mudpie with lava stones". It usually starts with "how do I make a more attractive mudpie?" There are countless ways of doing so. You could use marbles, leaves, different mud, different levels of consistency... But maybe using lava stones gives you the most bang for the buck. So then you are really filling a patent on "method and system for increasing mudpie attractiveness".
The infamous Amazon one-click patent can similarly be viewed that way. The patent is not really solving the problem of "how do we enable purchases with one-click?" (the solution to which is blindingly obvious) but of "how do we get people to buy more things on our online store?" Now, the path from there to "one-click buying" may also be obvious, no doubt, but it's not as obvious as the path from "how do you build one-click?" to "here's how" simply because the solution space is so much bigger.
In your case, I think you argue that there is nothing special about lava stones, and in fact, dirt/mud contains many stones. Probably, including tiny lava stones, whose only real difference with the additional lava stone bits is size.
So, adding stones is not very novel. There's also not much difference between a lava stone and a non-lava stone; if I can put in a non-lava stone, I can probably just as easily put in a lava stone. Is it not obvious that if I can put a quartz into a mud pie, I could also put a lava stone?
I guess the general strategy is to find the more general pattern and then show that the patent is just a specific instance of a larger, known pattern.