That sounds pretty good. You could start with a "basic care and feeding" section for people like the OP who are handed a fully set up Di2 bike but haven't been given much instruction. So as you said, things like charging and checking the battery, button and light functions, the different shift modes, etc. Then basic troubleshooting or FAQ covering things like crash mode, unexplained battery drain, accidentally changing shift modes, etc. Maybe front and rear micro-adjust, if that doesn't fall under the basics. Then moving on to eTube topics.