Maybe a crazy suggestion but why not make this the official editor? I’ve yet to use it but it seems nice and if that poll from May is anything to go by the current SDK is at least missing something. ( What IDE do you use? (2017) )
The current official SDK only wins if you include basic Netbeans, meaning that about half of those users aren’t using the features that the SDK comes with and if I understand it correctly, the spaceshift editor is directly focusing on those.
Unity also needs an other IDE if you want to write code and considering that that engine is rather popular having a similar setup for JME shouldn’t be a problem.
Again, I have pretty much no experience with JME as I just lack the time to make a game so there probably is something I’m missing and if I am feel free to call me out on that.