fwiw, silabs has integrated their isolation technology into an isolated shunt monitor Si8920, signal delay measured in nanoseconds.
http://www.mouser.com/ds/2/368/Si8920-766188.pdf
-100 to 100mv range
shunts are what tesla uses for fast and accurate.
It is conceivable to run an op amp and an isolator off the high side driver supply as well and blast out a digital current shunt reading back to the controller, or do other distributed gate logic stuff (i.e. hysteresis current control, shoot through protection, saturation detection, "formal" digital protocol between gates and controller, etc). I mean if you can have an attiny just to make a square wave, you can throw a $1 arm 24mhz 12bit adc on the high side gates and slave the low sides to them with another isolator, and even capture leg vs "neutral" voltages between pulses, or?? for pennies (shunts are cheap)
the controller basically then is the clock/position source plus user demands, and reporting back to user.
just my $0.015