WPCloudDeploy is a WordPress plugin that allows you to easily deploy and manage your own dedicated high-performance WordPress servers and sites at any cloud server provider.
It seems to me that a toggle switch under the Tweaks tab would be a great place to enable this per site. Perhaps this is too vendor-specific to warrant such precedent, but Cloudflare is fairly ubiquitous...
NGINX needs the following config in order to restore the original visitor IP when the site is behind Cloudflare:
The IP addresses need to reflect the lists from https://www.cloudflare.com/ips-v4 and https://www.cloudflare.com/ips-v6. There's a nice, scripted mechanism for this available here.
It seems to me that a toggle switch under the Tweaks tab would be a great place to enable this per site. Perhaps this is too vendor-specific to warrant such precedent, but Cloudflare is fairly ubiquitous...