CA, Kodi is already integrated into the Retropie build. I have had good luck wih Kodi. Perhaps I dont use too many plugins.
Autowiz, are you providing any controllers for the pie? The iBuffalo Classic USB gamepad is one of the better controllers, but the price has climbed to about $17.00 each. I use my wireless (bluetooth) ps3 controller. But I like the look / feel of the iBuffalo better.

EDIT: maybe provide an off button so that the OS does not corrupt from a quick power removal (i.e. pull the plug)