A small thing:

Its not quite all races, every race. Some races don't have any last start winners. In that case, no bet. That's why there's some races missing in the selections above.

If you want to reduce the number of races to bet on I suggest selecting races at random. If you set parameters like "Fewer than 14 runners" you change the mix of selections. And the method depends absolutely upon getting a felicitous mix of the good, the bad and the ugly (with the good predominating) - see selections above. If you take any steps to change that mix, won't work.

In the long run though I suspect the success or failure of something like this will depend upon finding a mechanism to select fewer races that have the same mix of selections but targetting the better prices.

Cheers

Hermes