If I understand your question, you are trying to provide users of your website a way to opt out of MCID tracking and therefor not have the AMCV cookie written to their browser. Is that correct?
yes: that's it!
Alright and can you help me to understand why you are trying to setup this opt out? For example, are you trying to comply with a particular privacy law? Also, would an opt out mean that the user is not tracked by any Adobe solution and thus no Adobe solution beacons should fire or is it specific to MCID tracking?