We ran into a similar issue once with a customer wanting to hang a 60" Pioneer above a HUGE fireplace in an A-Frame home. It was about 3 or 4 years ago, so the TV was very heavy, and the height was about 14-15 feet, which was far more than we were comfortable carrying up two ladders.
What we ending up doing (sorry I don't have any photos handy) was securing eye-loop rings through the top two mounting points on the back of the TV. We then bolted in heavy duty eye loops into the joists in the ceiling, form which we could hang pulleys. From there we ran stainless wire over the pulleys and down to the TV, and simply had two people lift the TV up, and a third just pushed it backwards onto the mount. Take the pulleys down, bundle up the stainless line, put some dark paint on the eye-loops in the ceiling (to roughly match the color) and we were good to go.
Made it super easy, and felt really safe. The owner has all the hardware stored in the garage, for when it comes time to reverse the process.