Not easier, but also not immediately harder because I've been maintaining compatibility with Blue Iris 3.66 for the past year and backwards compatibility with most of 4.x comes along with that. The difficulty comes with time, as more and more people get stuck on an ever-increasing number of old Blue Iris versions. You of all people should appreciate how many little and not so little problems this could cause. Even if I went to the effort of saving a list of "trusted versions" (which I am not going to do), only a handful would pay attention to that and it would be no guarantee of compatibility.
What if you cooridinated with BI developer, basically together you would be able to define a stable version which BI would also bless as stable. And that is the version you build your tool off of. Because of my limited experience (2 basic systems) I admit I don't comprehend the big picture you are faced with. Though I have wondered if there is such a thing a stable BI version that is uniformily stable for every PC/Camera combinations.