I have never played the MC titles so I cannot comment on any of your discussion above, however many players consider that any tactic that the games engine allows you to perform is legal and hence cannot be considered cheating and I would urge caution in using that term in this situation, gamey yes but cheating no.
Many players lay the fault at the feet of the game engine and game designers as they have not taken steps to prevent such tactics being used once they have become common knowledge, others state that players should restrain themselves from using such obviously unhistorical tactics and not exploit flaws in the games design.
Some play these titles just a pure game where "anything goes" and there is no such thing as gamey play and others play these games as historical simulations where they expect their opponent to play as such.
So as there never has and there will never be consensus across the whole community on these subjects (and boy we have had some mega threads on what is/is not considered gamey for example) if you don't like how your opponent plays then best end the game amicably and don't play them again.
If historical play is very important to you or a certain tactic makes your blood boil then it is best to discuss this before you start a scenario with a new opponent.