number and distribution of registrations maybe - that comes down to number and sizing of servers and geography/network diversity, the others are at best operational concerns for the backend, not for the "frontend" DNS servers.

backend/frontend?

Taking RFC 2870, why wouldn't all of section 2 and most of section 3 and section 4 be applicable to both gTLD and ccTLD servers (changing root zone and IANA as appropriate)?

sure, you could take those sections as a starting point. But why stop at TLDs? Why not make this applicable to -ALL- dns servers? The problem we tried to tackle with RFC 2010, and apparently not well considered by the authors of RFC 2870 is the difficulty of segmenting system availabilty from operations. So to clarify, are you talking about the server operations or are you talking about availability of the zone? RFC 2870 muddies the waters here. You seem to be leaning toward ensuring availablity. RFC 2010 attempted to make the distinction. gTLD servers, today, have an operational requirement to run on 64bit hardware. Few if any ccTLDs have that as a requirement. The root servers may not see that requirement until 2038 or so... In any case, RFC 2870 is getting long in the tooth and