Connect own nameservers to CloudFlare like DigitalOcean NameServer "NS3"

Hello,

I want to resell DO droplet from my own interface, and I have a question about DNS servers. I want to use my own-branded nameservers to my customers with the option to customers to create they own dns-zones from my interface. So first I wanted to setup 2 droplets for DNS in different DC’s with cPanel DNS-only in cluster-mode, for example. But looking to the future, I thought that they would not withstand a large number of DNS zones for clients. Next, I researched DO nameservers (ns1.digitalocean.com, ns2.digitalocean.com and ns3.digitalocean.com). Ns1 and ns2 in DO have their own dedicated servers with static IP’s, but ns3.digitalocean.com, as I can see, connected to “cf-198-41-222-173.cloudflare.com” host. But in CloudFlare we can’t use own-branded name servers (we can use it on “CloudFlare Business” plan only, for $200 each website). In CloudFlare for using own nameservers in cheaper way we can only use CNAME setup through they support. And I have a CloudFlare module for my interface, so my customers can manage they own zonez in CloudFlare from my interface too. So, how can I connect my own nameservers to CloudFlare as DigitalOcean’s ns3 with option to my customers to manage they dns-zones? Can I setup 2 droplets in DO with cPanel DNS-only and CNAME them to CloudFlare, will it work correctly? How does it work in DigitalOcean?