You only need to have the leather armour building around when you start each tech. In between times you could replace it with another building. A cottage would be one good example. Granted, this is still less than ideal from the perspective of many players, but if you are looking for something useful to do with that building slot while research is completing, it's one idea.
As for whether the effect of that dependency was fully anticipated ... it's an interesting question. The researches in question are mostly pretty short, so maybe they thought it wouldn't matter much. I suspect that in the future people will probably plan their plans around this contingency; like the requirement of Storehouse 10 for the Outfitting research, it will not be terribly disruptive for people who are building new cities from scratch in the way that it can be for people with maxed out cities.