I am an applied mathematician. A very simplified outline of my situation is as follows:
The leader of my research group is a "big wheel" in his specific research area. His contributions are considered both important and very demanding.
Recently I found a way to get a simplified access to one aspect of his work. I am very sure that no more than a few dozen people have ever made the effort to dig through this and understand it. The simplification is substantial, and even to my group leader it has not been known. Certainly it is not known to almost everybody else.
Other than an alternative simplified manner of setting up the theory, I can round out some things that have previously been done by hand-waving. That is only of theoretical interest.
So I wonder: finding this has been difficult, and it would help other researchers to know about it. But is it worth being published, with only a "sugar glaze" of actually -new- results? How can I determine this? How low for a journal should I aim?