I do not believe it is currently included in the cloudflare plugin, but you may want to ask IW if they could include it
I am not too sure exactly how your wanting your DNS to work, and apologies, I have not had time to read your link, so from a blind perspective, do you mean you want cloudflare to server your DNS for domains
Yes. Authoritative DNS would then be done on their globally distributed platform instead of my single box. Faster response times, better availability, better DDoS protection.
It is my understanding that I can still manage it in Interworx, but that the actual serving is done from CloudFlare. Well, that their API allows that. Not sure how to use it if it has been made available.