Do it. I’ve done this for 2 homes (moved up header to convert from 7’ to 8’ doors). Did it to clear a boat windshield, but the openness with the door up is great. You carry a ladder out without clipping the door when up. Looks more proportional too.
I have a 24' x 30' detached garage in northern MI that I use for storage/workshop etc., It has no AC or Heat and I don't plan on adding (I also have a heated attached garage). About 10 years ago I insulated the 2x4 walls with fiberglass bats and then closed them off using exterior grade siding...