There was several attempts to produce aircraft where half of the horsepower would've been pulling the aircraft, and other half was supposed to push it. Like the Fokker D.XXIII, Do 18/26/335, Marton XV, Short Singapore; the flying boats listed saw actual service.
So, for the sake of discussion, lets asume that some if not all of the major air forces introduce a 'push-pull' combat aircraft on large scale, from late 1930s on. What roles should've been tailored for, what to cancel instead, who should've benfitted the most? For what roles and/or countries it would've been a bad bet?