How to associate a custom post type with groups.

Hi, I'm trying Buddypress for a set of events that happen in different cities. For each city, I'd like to create a Buddypress group for that event. Weeks before each event, I need all the participants to make topic suggestions, and be able to comment on them.

(In the long run, I need this suggestion feature, searchable profiles with custom fields, and event management/ticket sales. That's why Buddypress is under consideration. In terms of scale, we'll see 2-3k users this year.)

Here's what I'd like to see: if a user joins a group called "London" for the London event, they'll see the Home and Members tab, plus a Suggestion tab. If they go into that tab, it looks just like the activity tab but only shows suggestions. From here, they can make a suggestion, and see other group members suggestions which they can comment on.

I've been looking into multiple ways of doing this – no luck with any so far.

I'm not sure if this is doable with existing BP plugins, which would be better. Or, if I'm better off doing this on WP without Buddypress (given my needs above.) Suggestions in either of these directions are welcome too.

I've setup Suggestions as a custom post type, so if that could be listed as a Groups tab, I'm done.

Or if I could add another type to the activitiy stream (currently GRoup Memberships, and Updates) and then create another tab where that drop-down was the default, I'm done too.

If it'll require coding, I've spent some time with the BP Skeleton plugin, but it seems that I might need to extend BP_Groups_Component, not BP_Component, since I want to change the nav for each group. But I still haven't found the right way. Overriding setup_nav() doesn't work. Hard-coding changes to $bp->bp_options_nav doesn't seem workable since the array keys I need to access are user-generated (the group name)

I'm a PHP coder, familiar with writing basic WP plugins and themes, but not Buddypress. It would be great to know if I'm on the right track – any suggestions appreciated!