Hello,
Seeing as the ECU's are low cost and they are also high current / voltage / power and they also protect your expensive Lipo batterys etc I would recommend using one of these from off the shelf.
Also to control brushless motors involve quite hands on coding unless you do it in a bit banged PWM method which will not work overly well. Some of the PIC chips come with analogue brushless motor driver hardware built in but again the coding for this peripheral combined with the external power mosfet circuitry involved means that an off the shelf device will in the end save you time and money. And maybe hair too
If you do want to proceed with making your own ECU then you should refer to Microchips application note on the subject.
http://www.microchip.com/stellent/idcpl ... m=en542235
Sorry to put you off, if you do decide to go ahead then let me know as I would like to hear on your progress.