So I sold the house, and we have closed.
Things I did and learned:
No one had much interest in the cameras or security systems while shopping, no questions, etc. I'm sure they noticed them, but it was not an issue while selling.
It also was passed over during home inspection and all the acceptance periods in the contract.
I had at this point removed the PC serving as an NVR, left the POE switch, and left the entire Elk panel in and running and connected to Alarm Relay.
As we approached closing I think they started to worry, and asked all sorts of questions. I wrote down a lot of details, and showed up on their final walkthru to show them how to download the panel configuration with elkrp, where to get software, shared account information with Alarm Relay, etc. The guy's eyes glazed over a bit but they did not complain. I offered to answer questions later.
Since close have not heard anything.
I was very careful, in writing, more than once to explain that the panel powered the smoke detectors, and that there would be no fire protection if they did not keep it powered and working (monitoring aside). Including telling them again in front of both realtors. That was my biggest fear, that they would power it down and a fire would occur. I was also careful to tell them in writing it was done by the home-owner, and we made no representations as to whether it met code or worked or anything else, it was just as-is. Because Florida has way too many lawyers.
But... in the end, the whole alarm and security camera set up was not a significant part of the sale of the house. I don't want to say I worried for nothing, but I think I worried more than I need have.