You can’t do that, because it makes no sense. The proxy causes Cloudflare IPs to be returned in DNS, and Cloudflare does not have any function to vary these DNS responses based on the requesting IP. And indeed, even if they did, this would break the moment a DNS client uses a recursive resolver, especially one not supporting ECS. ECS is not widely supported due to privacy concerns, and recursive resolvers are in use by almost all systems.