Your solution fits a rather narrow gap of the market.
The first part of the market is where a brake is not needed - the motor propelling devices where standard operation friction is enough to stop them when unpowered. It's a very broad domain: motor being non-critical, say, powering a fan which is harmless when allowed to spin down slowly after switching power off; high-torque (heavy industrial) machines of moderate inertia, that will stop within 1-2 turns by themselves without constant power input, machinery where duty cycle of motor operation is so long comparing to switch on/off times these become negligible (pumps operating on large reservoirs) and many others.
The other side of the market requires braking far more efficient than a couple resistors can provide. These will use mechanical clutches or external mechanical brakes that can stop the rotation within much less than several rotations, and inhibit slow free rotation (your brake does nothing against that!) - this will be safety equipment stopping machines that can be dangerous to life and health: saw blades, elevators, heavy machinery of high inertia that would take a long time to sink all the stored momentum through the resistors, vehicles and transport devices (cranes/gantries), also production lines where a fault at a point could lead to serious accident if allowed to propagate down the production line with damaged product.
You're in a narrow segment where a weak brake like yours is sufficient. It may be budget machinery which allows a delay at braking at expense of safety; it may be very heavy, high-inertia machinery where rapid mechanical braking is simply impossible due to forces involved. It may be also a comfort/efficiency feature for devices that don't require brakes, but presence of one allows faster change of operation - say, service/regulation access to a section of a machine that is locked out for duration of operation.
And even in these cases a segment of your market is stolen by controllers that have your feature integrated, and provide it as a part of control, not just extra safety.