Been done Duncan.
The Seig fit the brushless motor and driver board to some of their machines.
Few years ago I had the first ones to test. Told they were bomb proof so I thought the best way to test an over load was clamp the spindle to the column with two big steel straps and clamps and switch on.
Wasn't my mill was it ? 
Bang.
Sorry.
Could you try again ? Eventually they came up with a board that works. Overloads it just switches off and 10 seconds later after you have removed all loose fingers and bits of cutter and steam chest it will restart.
Brilliant except when this was pointed out the short armed, long pocketed Muddle Engineers all screamed too expensive and we now know how to repair the cheap boards.
Can't win can you ? Some days it makes you wonder why you bother as well.