Mikko, thanks for your comments and your plug-in!
From an outsiders perspective, it seems like this would be a great enhancement for CB. It could be a flag on the drop down field during the Admin field definition that says another method (e.g. ajax) is used to generate the field data so CB would not populate the field with the values during registration. It could still do the server side validations, etc.
If that was combined with an AJAX Conditions during User registration it could solve a lot of problems.
Of course I know nothing about the internals of CB or its development process, but I'll throw that out there for the CB wish list.
As it turns out, after discussing this problem with my project manager, he is willing to populate the field values as they become available instead of all at once .
This is great news for me since I can use the existing conditions plug-in for the foreseeable future. I would still like to assist in such a project so if anyone is up for it, let me know.