Just a personal opinion but, as already pointed out by several above, the current system is the best way to go. Using separate units of measurement for speed, height, RVR/viz etc. avoids misunderstanding and the speed with which the current, commercially orientated, flying schools are churning out new pilots these days I'm all in favour of as many built in safety devices as possible. Happy to see there is no serious effort by any major aviation organisation to change the present, western system.