Pete,
The problem comes when one must impute the size of the target. Over here, we all go by inches. But I'll grant you that if one knows the target size in centimeters, your system can work well.
Let's say you're looking at a 42cm target.
First of all, you'd have to be able to determine whether you're at .3 mils, .6 or .7 mils, etc., on the reticle. Let's assume you get that part perfect: The target is .6 mils in height.
Since it's a 42cm target, you'll be doing this:
Height of item in meters x 1000/Mils read = Distance to item in meters
This target is 42cm, so it'll be .42 meters. Okay.
.42 x 1000/mils read
is
420/.6 = distance to target in meters (which is 700 in this case).
So I'll go along with you if we're doing everything by the metric system.
Over here, however, we've grown up using our own crotchety old system of measure. We'd end up having to convert inches to metric if we were to make good use of the mil reticle, which would defeat our purpose.
Too, with MOA graduated turrets, we'd lose the compatibility of the reticle and turrets. I know that the scopes made over your way will have mil graduated turrets, which is good if your reticle is a mildot.
I would not argue that for a "metric minded" person the mil reticle will work--although I would effectively argue that a mil reticle such as the Leupold TMR or the Premier Gen II will be the best choice for ranging, since they have hash marks which disect the mils...
Dan