my opinion on the gTLD zone file access system
I run a website hosting, design, and domain registration business. I do not own a registry, yet. I currently download 13 zone files daily for statistical and monitoring purposes. The current system does have some minor drawbacks which would become worse as the number of zone files increases. For myself, the main drawback is the zone file structure. The zone files I download are structured in different ways, so I need to make my processing script work differently for the different structures. Not a big deal with 13 zone files and 4 different structures, but if new registries come up with their own structures, more programming will be needed to process them. There are other problems with the current system to consider, but to me, most of them are trivial, even as new TLDs are added.
Some of the problems and solutions for users are related to ease of access. Personally, I don't think it should be made easy (as in 1 step) to get all zone files. That just makes it easier for those who abuse them to have more to abuse. I think each registry should have some control over who they give access to, and even whether or not they want to make it publicly available. As Michael D. Palage stated, some registries may have legitimate reasons to not want to make zone files available publicly.
In my opinion, the Enhanced Bi-lateral model may be the best choice. By standardizing the different elements, it makes the whole process simpler for both the registry and the consumer. With standardization, new registries will be saved some of the work involved in setting up their zone file system.
As far as the 3rd party approaches, if one of those is used, I think the repository model would be the best choice.
With the clearinghouse model, its main purpose is to relieve registries of the burden of setting up and dealing with zone file access accounts. I'm not a registry owner or operator, but I think the volume of ZFA accounts is pretty small relative to the number of domains they deal with, so if I ever set up my own registry, I don't think the process of setting up and managing accounts would be an issue of concern. If I were to deal with zone file access through a 3rd party, I think I would prefer to deal with just that 3rd party. That's why, in my opinion, the repository model would be the best 3rd party choice. With the proxy model, I would be dealing with the 3rd party as well as the end users. The proxy model may have its advantages, but overall, I would prefer to do one or the other, deal with the users, or deal with a 3rd party, not both.
I think the best option would be to standardize the zone file system, (Enhanced Bi-lateral model), and implement the repository model, then let registries choose whether they want to deal with the end users or one 3rd party company. The system does need standardization, but beyond that, it should be what's best for the registries.
I am not a registry owner or operator, so my opinions are those of an end user. I think what we need here are some opinions from some of the registries that will be affected. What would they prefer to do? They are the ones who will be affected the most by whatever choice is made.