I don't recall what the hack is. I have tried to keep Lemur working with only the stock JME shaders, though. It makes it easier for folks (like yourself) to swap them with their own because behavior is well defined and consistent.
And yes, the double dipping layout concerns me because on paper I can create situations where it needs to be a triple dipping layout and then a quadruple dipping layout. So to me it isn't to "double dip or not" but to "go full on iterative layouts" and bring with that all of the complexity.
I'm super glad it works well in all of your use-cases, though. And that's the benefit of open source.
So, yes, if your drop down is tied to all of that then it's probably more work to make it "core friendly" than it's worth.
Still not sure if OP means a drop down menu or a combo box, though. One is 5 lines of code and the other is a bit more complicated.