I have no problems with any other ratio and I picked 14.7 more or less arbitrarily. But I figure for real world use knowing the emissions output is kind of helpful so deviating from 14.7 usually carries along with it extra emissions. For setting up an experiment I see no reason why it could not be tested in 0.1 increments from 10:1 to 100:1 as long as the results are repeatable and able to be duplicated.
Really after thinking about it, setting up some sort of test rig that can measure the energy output of any desired fuel in a consistent fashion might be a very handy thing. There are lots of additives and junk that could also be tested in that apparatus and could settle a lot of debates on here.
Off the top of my head, HHO, H2, water injection, acetone, toluene, little bottles of stuff from the store, and different brands of gasoline. If someone could come up with a way to measure energy output, all those could be tested easily
