Some sort of management interface is going to be important. You'd also need to have the domain names divided up to the owners of them and provide a way to manage A, CNAME, MX, and TXT. It might be easier on my end just to write a new application, because I've had stupid problems trying to figure out how to add content to special pages in MediaWiki.
I've made a domain look up for it, which could be connected to by such a web application for users to add contact information for their domains. I've heard something about making your own whois server the way you can make a nameserver, which might be preferable to just a web database. I can also hide various fields for the contact information; I might leave out the entire billing section since it's not needed for a free domain name.
http://www.whois.ssu.lt/One thing that I might add to the application would be a way to approve accounts before they can register domains after they give a reason so that I can prevent spam on a free service and keep it to domains for Warhammer 40,000 websites.
I just made a project on GitHub for anyone who has any interest in working on it.
https://github.com/Sturmkrieg/LinodeDomainRegistrar