I would imagine whoever bought it would write a clause to say he can't create anything similar in future.
Nova LauncherEdge Gestures as an alternative to android gesturesQuick Cursor for easy one handed usagePanels as a sidebar based quick launch / app switcher AccuWeather for weather and minute by minute forecast Google Fit for basic quiet step counting - can also measure your heart rate with the cameraOutdoor Active or AllTrails to show you walking routesStreet Complete to contribute to open street map in a much friendlier way Spark for multi account email
What apps did you struggle to get working as expected?I do grant that unfortunately due to the distro and window manager differences there can be issues with graphical inconsistencies and integration into the system (file associations for example)
I would imagine whoever bought it would write a clause to say he can't create anything similar in future.