Golfsmith do a 15° Hi-COR driver. There is no current limit above 15° that I can find. Some searching on FGI produced some interesting information, seems the theoretical COR limit is round about 0.92. After that chances increase that clubfaces will be so thin, they will break.
As for fairway woods, to maximise the COR often means increasing the clubhead size to accommodate a bigger face - and who can hit a "bighead" fairway wood? Yes it'll be Hi-COR but might be unplayable, which kind of defeats the object of the exercise.
Although I think the the Ashton X-1 achieves Hi-COR without being excessive, I'd have to do more digging around.
As for 3W off the tee, what you gain in COR you might lose in launch angle/spin rate, so it's no guarantee of distance gain.