my challenged friend is a great partner,...
my challenged friend is a great partner, but doesn't offer confidence for me to lead. would this be a safer option for him lead belaying?
Yes, much better than an ATC or a figure 8, as far as being dummy proof goes. It's not as easy to pass rope through as an ATC or 8 though, so if you climb fast, he may have some trouble getting enough slack out for you. And if you fall you'll probably jerk to a stop quicker, since Grigri's catch immediately. But all in all, it would certainly be safer.