You know, I've always thought that in a kendo vs fencing match, it'd be more appropriate for the kendoka to wear fencing armour, and vice-versa, because the mengane is too wide to stop a foil/epee to the face, while fencing helmet is too flimsy to really withstand a men, or protect against a tsuki. In which case both players would be at grave risk, and fighting with one hand tied behind their backs.