No that is not the fix. If you add enough right thrust for a steep climb it will be too much for cruise speed, enough for cruise then not enough for climb. Models fly exactly the same as full sized aircraft. Yes you can get closer to the ragged edge with models and eliminate some quirks but otherwise the aerodynamic principles are the same. For the record F/S aircraft also fix these same issues with right thrust and even a slightly canted vertical stab. The problem is, P-factor is transitory and varying so there is no magic fix, for F/S or models. Pilot input is needed nothing else will fix it. Remember he has a scale aircraft so it will react more like the original, you can design a model that lessens the effects and they tend to be the sport and stunt planes that are not scale replicas or are replicas of high performance aerobatic A/C that have done the design work to lessen the effects. Put a yaw meter in one of your planes and you will find your plane does not hold yaw nearly as well as you believe.