Can the word "diplomacy" be used to refer to a particular form of diplomacy or diplomatic strategy?

Solution 1:

It's perfectly acceptable. A genitive NP marking a specific style of diplomacy can readily be found in high quality English, therefore it's grammatical.

Trump's diplomacy is hardly the only part of his presidency shaped by his experiences with golf courses. (Washington Post, 2017)

The two distinctive contributions of the Conservative Party's diplomacy in this century have been at the time of Suez when we committed aggression ourselves, and at Munich where we supported it in another. (British House of Commons, 1960)

Even those allies who supported the United States complained privately about the paucity of consultation and the ineffectiveness of the administration's diplomacy. (Foreign Affairs, 2003)