Every once in a while, I will see a reddish-brown "klinker" in the touch hole, which I assume is poorly-burned powder or some related kind of trash. If I try to shoot the gun in that condition, it often won't work. So when I see it, I dig it out or shift it around so that fresh powder appears, and that always allows the gun to go off. I suspect those little klinkers are responsible for at least some of the flintlock's reputation for unreliability.
Tl;dr: I think big touch holes are a very good idea.