I did some research into this for x-plane 10 awhile back and even went back and forth with Ben in emails. What I finally discovered was that one needs to tweak a value in the scenery file itself to get distant lights to render. This was the only way I could do it. I only tested it on a few files, but it definitely worked. I don't recall what exactly the change was, but I'll try and look into it for XP11 as I only recently installed 11 and was shocked that this issue had not been addressed. I'll post my findings.