I am surprised that there were no other complaints sooner but for a long time it was not possible to specify instrumentation test runner and our plugin always used the default one. Well, this is changed now and you can customize this for your Android Test projects in a 'Run' tab of project customizer.
Future improvements are possible but at least the simple support is now enabled. Adding suggestion based on AndroidManifest.xml parsing can be added. I also have to thank Rob Smith for his input on this.
Note: the updated version is available from an update center announced in previous post.