I think that there might be some confusion of terminology here.
In canonical GTD, a "next action" is the single next thing that can be done on a project to move it forward. What I hear you saying, Mike, is that you have projects where there are multiple things that could move the project forward. This is a parallel project in the current OF implementation. But what is missing for you is the ability to filter the parallel actions in a different way. Suppose I have a project like:
Code:
Migrated to OmniFocus
Share OO to OF script Context: Web
Write script to check for missing next-actions Context: Coding
Migrate work items to OmniFocus Context: Planning
Migrate templates to OmniFocus Context: Planning
Currently, the Available filter would show all four actions and the Next filter would just show "Share OO to OF script". As I understand it, Mike, you're looking for a "Next by Context" filter that would show just the first three actions. It would omit the fourth, because "Migrate templates to OmniFocus" is not the next action in the Planning context.
Do I understand what you're looking for?