Here is a summary of the existing assignment subtypes and whether they would be supported by the proposed submission-plugin model.
Collaborative real-time editor
Online Audio Recording
Comments: This assignment type is about a semi automated workflow for providing randomised instructions to students via files.
Comments: This assignment is about an interactive editing interface for providing feedback files to students.
Mail Simulator Assignment
Comments: The email submission component could be supported, but not the feedback.
Comments: The only bit I don't think could be done right now is this: "When at least one comment is made on each of the other group members reflections, the student will be able to confirm them self ready for grading." - but we could change the API to allow a plugin to control if a student is allowed to finalize a submission or not.
Comments: This is similar to the Reflection Assignment type but without the reliance on a discussion forum.
Team Assignment Type
Comments: This will be built into the core module
Comments: The code could be submitted to the judging server when the submission is saved. The view submission could then show the results of the compilation/unit tests by loading them from the server - or the server could post the results back into the gradebook via webservices.
Summary: From the list here there are 5 Supported (or will be builtin to the core module) and 5 unsupported. However if we add support for "feedback" plugins as well (same idea as submission plugins except they are shown in the feedback block for students, on the grading page for markers and can add to the intro section for an assignment) then we could support the other 5 as well. I'll write up something about feedback plugins soon.