It will be reasonably difficult to implement as a maintenance free system but would work. (not my first choice)
It does lend itself to using variable pitch swashplate drive for the genny, to achieve a torque converter... and that would give you an MPPT built in. (just control the swash angle as you would by computer excited coil as with an excavator pump drive system).
From a practical perspective, the normal way is simpler to implement, with less losses, but the wind is free and if the hydraulic lines and components are too, then there is nothing stopping you really.... as it is really a normal system, with all the hydraulics thrown on top.
You could also bring the shaft power down to ground level via right angle drive gearbox and long drive shaft, rather than hydraulic line, as they do with the Turbex
http://www.turbex.co.za/Documents/Generator.htmlSo the hydraulic system will work, but not the easiest way to get power from the wind, even if you bring the power down the tower as per Turbex. They do drive a pump (water), but even they use a generator direct from the drive shaft at ground level
The acid test is.... does anyone do this hydraulic angle commercially? and if not why not?
Perhaps there are just better ways.
............................oztules