Oh, one cheap solution to the spotter with a reticle, is to use a scope with a reticle to do your spotting, you will give up field of view but if your using it to spot corrections on targets then a huge field of view isn't necessary. All you have to is get a cheap picatinny rail, under 15$ from amazon, drill and tap a hole for 1/4-20. then mount a scope onto the rail as usual, then screw a tripod into the hole you tapped.
As far as using mil reticle to get accurate ranges at long range...good luck. Its not as easy as everyone makes it out to be. It requires previous knowledge of actual target size, coupled that with using reticles that may be to thick to get precises measurments, as well as a sight picture which is never perfectly still. They guys who get trainned to do this and spend hours and hours doing it give them selves a 5 or 10 % margine of error. So at 1000m thats a 100m meter error. Thats a pretty big miss.
If your using it just as a ball park measurement to shoot at natural targets very far away, and your going to make corrections any way, then yeah use mil ranging.