With todays electronics varying the speed of the rotors to control the output is a bit redundant.
Why not look at a full BOOST/ BUCK citcuit so you can use more of the energy from the generator (they do exist).
If you are looking at getting the most from your wind turbine this would be the way to go.
The problem is you have to find the point where your generator can supply current at a working voltage.
I tried a boost/buck on a 40 watt solar panel and set it to a max of 1.5 amps at 13.8 volts (20watts). What happened was when the pannel dropped below 20watts the unit tried to draw more and shorted the panel out. So a way to reduce the current demand is needed. Hence MPPT.
The only reason to monitor tip speed should be to stop the turbine from flying apart.