I currently do this by exporting the font and printing the waterfall from InDesign, but would love (and smoothen my workflow) if this was a simple checkbox in Glyph’s own printing output options.
If you don’t have to print, there is a plugin that shows waterfall (available from Plugin Manager).
Otherwise, I think this sounds like a good Drawbot project.
Stick with it. That is much better because much more customisable. And more relevant result, too, because Glyphs can only send the outlines to the printer, but you want to see how the shapes behave as font.
I see, I see. I was mostly thinking this from a ease of use point of view 
Often enough I’m printing from glyphs at several sizes, thought it might be something more people have asked before or might be interested in. I do see your point about the technical verification from using InDesign to print it.