Did you have a chance to read the article that goes with the chart you linked to? It's worth a read: http://aem.asm.org/content/64/7/2616.full.pdf
When you write 60%yeast/40%Acid, I'm guessing you mean 40% Lactic Acid Bacteria (LAB), right? LAB will always outnumber the yeast - by as much as 2 orders of magnitude (100:1). The likely range of microbial makeup is probably 99% yeast/1% LAB -- 90% yeast/10% LAB. Cultures closer to 99% yeast/1% LAB are more common from what I've read. This is of course keeping in mind that the starter or dough is mostly flour and water and that the yeast and LAB combined are but a small fraction of the whole. I'm sure that you can effect the yeast/LAB makeup by manipulating the environment and food supply, however, the specific microorganisms present will also be a determining factor.
In the 2 culture test you propose, I'm not sure your hypothesis is correct. If you have manipulated the starter to favor the LAB over the yeast, once you introduce it to the dough, the microorganisms will do what they naturally want to do unless you also manipulate the dough to continue to favor one or the other - in which case, everything else is not equal as you propose in the test as you will have to manipulate each dough differently.
If you want a more or less sour dough, I think you have several general choices (or a combination of them):
1) Get a starter that in and of itself produces a more or less sour crust. Not all cultures behave the same.
2) Use more starter that is already has a large acid buildup. This method, for example: http://www.pizzamaking.com/forum/index.php?topic=10237.0
Jus be careful - you can easily liquefy your dough with too much of a very acidic, enzymatic culture. This would be closest to what you suggest above, but it's a matter of pre-creating the acid - not necessarily manipulating the makeup of the culture. When you do this, you are also adding a lot of yeast, so further fermentation can be rapid.
3) Manipulate the environment to favor the LAB. You can exploit the gap between the yeast and LAB growth rates you see in the chart you linked to as I wrote about here: http://www.pizzamaking.com/forum/index.php?topic=14627.msg145628#msg145628
I've read that this favors the development of lactic acid over acetic acid. My results seem to support this - it is more creamy, mild sour as opposed to a sharp vinegar sourness.
4) Manipulate the environment to favor growth - microbes first want to survive. The more energy they spend on survival, the less they spend on growth. More water, less salt, ideal temperature etc. make it easier to survive, and they can thus use more energy to grow. The acids produced are a byproduct of growth.
5) Extend the fermentation time to build up more acid in the dough. This generally involves lower temps which should favor acetic acid buildup over lactic. With my culture, it takes something over 48 hours for the dough to become perceptibly sour. At 72 hours, the baked crust has a very distinct sour note. http://www.pizzamaking.com/forum/index.php?topic=14249.msg170880#msg170880
With respect to using a pH meter. It won't tell you anything about the yeast or LAB - just the pH (lower is more acidic). A lower pH would indicate more acid build up, but this does not necessarily correlate to the yeast/lab ratio. There are many other factors that could be significant.