That sounds like turbo lag to me more than throttle by wire delay. BMW says the AH3's step load delay is 2.25 seconds as opposed to 2.75 in the 335i, thanks to eBOOST.
High revs followed by the power coming in is pretty typical of lag. I think people are crazy when they say N55 has no turbo lag. It definitely has a little bit of lag, but only if you start off with the engine under 2000 RPM and apply full throttle.
OTOH even if the car immediately gave you throttle, I don't think it'd make the difference between dangerous vs safe. That only translates to maybe a few feet and 5mph of difference assuming the car could have responded with full power 1 or 2 seconds earlier.
If you want that, get a SRT8 with a naturally aspirated 6.4L engine or a larger displacement turbocharged car where even without boost the car has plenty of power on tap.