Issues with RSVP and Signup integration

First, thanks for this module. I'm currently considering it for a project that needs events which can:
1. Always allow invitations
2. Optionally allow rsvps/signups by application
3. Optionally allow open signups

It seems you've done a lot of work over the past few months to move in this direction, which is great. I think I'm running into a few issues when trying to use the signup connector module for events with invitations and events that are "By application only." I'd like to pitch in and help figure this out so that rsvp and signup integration can get to the next level.

Item #1: How RVSP behaves when Signups are disabled

Previously, I was also running into this issue where disabling signups would give an Access Denied when a user attempts to accept an invitation (http://drupal.org/node/531042). I've upgraded to the rsvp-6.x-2.x-dev version from August 1 and now I'm seeing a message along the lines of "Your response has been saved. Signup to denied. Signup is already closed." If I understand this correctly, the RSVP was saved, but the signup is closed. This message and this behavior can be a bit confusing.

After thinking about this for a bit, I'm wondering if a useful behavior of the signup connector might be that RSVPs should always go into signups, whether they are currently enabled or not. This might solve a situation where a user has some people that have signed up and some people that have been invited. At some point the user might want to close the open signups, but keep the list of people from both sources in one place. The big thing that would need to happen is to teach signup module to still display signup list once you've manually disabled it. This is probably an issue for signup. Based on the way you responded in the previously mentioned issue (#531042) you chose the method above because of how signup behaves when disabled.

Item #2: The RSVP and signup interfaces

I think I'm also tripping over how the fieldsets and check boxes for these two modules interact. Right now it's very easy for a new user to get lost. I think it comes down to two items: First, I don't understand what the "By invitation only" checkbox does. Having it checked or unchecked doesn't seem to make a difference in how the module behaves.

Second, it seems that "By application" and "Enable signups" should be mutually exclusive in most site configurations. Right now it's very easy for me to set up an event that has both actions. (I think there might be a fringe scenario where you'd want some users to be able to sign up and other users to be forced to submit an application, but that's might be a different conversation.)

Obviously I’m just getting my head around this, so please correct me anywhere I’m off. I’d love to hear your thoughts on how the signup and rsvp integration will move forward and if any of what I said above makes sense. Thanks in advance!