In the current system, a pilot can land as often as once every thirty seconds. This essentially means that the most efficient way to increase landing count is to do 180 turns. So the fastest way to get to higher grades is actually flying in a way that would get you a violation for acrobatics on ES/TS. A close second is CAK3-CZBB. Both airports do not have spawns, and it takes less than a minute to fly between them. So forcing the landing count to be on training would not work.
I am proposing to increase this half-a-minute limit to the usual time it takes to fly a traffic pattern/circuit. A good time would be between 3-5 minutes, not too long, so that a fast pattern still registers.