I didn't completely read the entire thread, however what about this:
A webpage hosted at jmonkeyengine.org with something like this:
a) a template in the background with the gradle files
b) Some HTML Forms for ProjectNames etc
c) Replace the Variables in the gradle file and offer it as download (maybe even zipped)
That way you only need to visit "jmonkeyengine.org/create_project" and download it.
However for "unexperienced developers": How should they run or even debug their project when they can't click on the green arrow? I mean installing git on windows is funny
So it would better to offer project templates for the "big three" IDEs.
Because: What is the profit to the average developer when using a seperate gradle?
Or how about dependency management? It's nice to simply add maven entries, however most people will simply download the jar's and drop them in.
so, mhh not an easy task
Edit: And yeah, linux users aren't the problem most of the time as you learn to work around troubles and use the command line