thats interesting. I looked at pictures. does it have a motor as the load for the test motor? I think this is a brushed system isnt it?

if you want to test a motor you have to simulate the acceleration loads and the work loads. a flywheel dyno is great for measuring power during acceleration but after acceleration it doesnt provide useful data. it does provide data that allows you to match inertia so that deceleration and acceleration can be tuned.

a load dyno can provide power curves and simulate the work that has to be done at a constant speed so its good for measuring power, torque, rpm. it doesnt help with inertia. but what it does very well is allow you to test the thermal characteristics of a motor under work conditions. this allows you to determine the max power a motor can deliver without overheating.

if you had an inertia and load dyno in one you would need to do less testing and math to understand everything a motor can do. if the flywheel matches the inertia your chassis normally introduces during acceleration you have 1 of 2 pieces of physics covered. the second piece is the friction and and efficiencies of the chassis which can be simulated by the brake motor (the second motor) resisting the same way tires and belts and ... does on a chassis.

but there in lies the problem. you can calculate the inertia and pick a flywheel to simulate. but then you have to determine how much power is lost between the motor and the wheels to setup the load motor to introduce those same losses.

If it were me and you wanted to cover these two pieces of physics I would get a chassis and add a load motor. you can run a fixed pwm to the load motor to simulate friction on track but its will be different for each track. it would also be flight cheaper to get a motor acceleration dyno and add a load motor that would simulate heat rain and road conditions.

in short I wouldnt convert a motor only load dyno over to brushless unless you are pretty decent with DIY. if you dont simulate the inertia under acceleration you are only half way there.

max rain-you may find more power and less heat if you come into a corner at 3000 and exit at 10,500 because the average corner speed of 7000 is your peak power. peak efficiency will be 15-20% higher so it would come out even cooler.