Many of our customers who had a control system (not installed by us) will never opt for a control system again -- especially if the control system was mostly used for watching TV and playing music.

With respect to A/V receivers and CEC, I've had mixed results and generally end up defeating CEC either by turning it OFF or using a dongle. The risk of mayhem increases when multiple devices are on CEC. A cable box update in the middle of the night can trigger system startup -- as can starting up a DVD player shared between rooms. CEC is sometimes tied to enabling advanced audio formats, such as ATMOS. Turning OFF CEC in these devices is not an option, but the CEC defeaters will usually work OK. Unfortunately, the CEC defeaters that I've seen do not promise to support high video bandwidth.

As mentioned prior, I'm debating about investing some time brewing up a Raspberry Pi accessory that monitors and corrects spurious CEC interactions. At best this would be a clunky solution because I could not prevent devices from issuing their CEC commands and other devices from responding, I'd need to monitor this and issue counteracting commands that may trigger reactions.