Breed to the....galloping style....

Galloping styles doesn't determine whether a horse will be any good. Plus there would exist conditions [soft,fast etc] where any type of action would suit. The idea behind using bloodlines is to reproduce winners, how they run is secondary.
There are far to many variables outside our control to make any breeding strategy sensible.

...In  other  fields...cattle, sheep....breeders  target  the  qualities  they  desire,  and  breed  for  them.  In  racehorses  they  don,t  seem  to  know  what  qualities  to  aim  for...seems   to  me....

The principle is the same in racing. A farmer would choose the ideal candidate from each generation to breed into the next, and cull those with undesirable traits. In racing the ideal candidates are champions[desirable trait], these are used to breed the next generation whilst those who are not up to standard don't get the chance. This process has been used for the past 3 centuries to get to where we are today.