Yes, I am writing completely independent modules with definition java files. I'm currently just running development and testing locally. Once I build my new module (which lists module-parent as its parent), I just drop the zip onto my MangoES. I'm currently working on two modules. One is a better and more standardized deviceConfig/templating module. And the second is a graphical gauges one which wraps ma-gauge and uses the DP tags to dynamically load different layouts. Like so:
The injector will be great. Should work out for me nicely.
At some point I will look at publishing my modules to the store. But they aren't quite ready for prime time.