Well Chrome I agree with your summation in it's entirity. I know that we will never know all the parameters in a given race, that's why I'm convinced that the only chance is a mechanical one. But it's hard to put into words,.. I'll try,

Say that we take all horses in given races with a given set of parameters (that are in our control) eg. recent runs, performed on the going, distance S/R senior jockey, Metro run, previous winner etc etc etc. you know...... a "system" dare I say? and then we observe that there is a consistent S/R over an extended period of time, for arguments sake lets say that S/R is 85% for the place and we managed to get an average divi of $1.30c (by betting at Best Tote etc )

Now this means that we have 15 losers from every 100 bets, hopefully INCLUDED is the ones where the jockey has a snorting problem, a trainer who is known to give some selected horses a bucket of water b4 the race; or ran him for 20 miles the day b4, the one who is unlucky enough to be targeted by the other jockeys etc etc etc, HEY NO I"M ONLY JOKING I'm sure none of that happens, it's just bad luck I know, heheheh! but you see where I'm coming from, we have to account for the mishaps within our failure rate?