As far as the question about internal nipples - correct me if I'm wrong, but wouldn't having a smaller hole in the rim at the nipple decrease the likelihood of cracking around the nipple? Seems with everyone making lighter rims (and especially on a version 1.0),a smaller hole (ie. internal nipple) would be a good idea as it would better preserve the integrity of the rim and better resist a nipple pulling through the rim. Nipple washers could be a band-aid instead. There is also the claim that internal nipples are more aero - but I don't know how significant that is... As a light rider, I very rarely have to true my wheels - so not the end of the world having to pull the tire off when necessary; if we were talking tubulars - I agree, it would be a real pain. Open to hear other thoughts on the matter.
Actually, this is wrong. A smaller hole may leave more material but a smaller hole creates a greater stress concentration (raiser). Fatigue cracks always start as stress concentrations. In certain situations, outside of bicycle components, we actually drill a larger hole when a stress fracture forms to remove the fracture and reduce the likelihood of another one forming. Anyways, spokes pull through rims due to this so making a smaller hole increases the need for reinforcement around the holes. In this instance, decreasing the hole size in half roughly means we need to make the material surrounding it - to a fast mental estimation of dimensions - about 35% stronger.