I am also looking to design a speed controller, and have thought for a while about this problem. The biggest issue is switching polarity based on the length of the pulse. I assume the Victor achieves this with a microcontroller, which also lets it have a deadband and the ability to be calibrated. If you don't want to get into that, you can do the following much simpler design. I haven't tried this, but plan to, and see no reason why it wouldn't work.
Have the PWM signal control the speed, but not polarity, of the output. This just requires some big FETs. Have two separate digital outputs control the polarity via an H-bridge. More info can be found here:
http://roko.ca/articles/hbridge.php?page=3