From the looks of the web page/link, that will duplicate functionality that already exists in the new system. There would be two places to put Writing Tips & Advice conversations, for example. Ditto for other groups/forums.
Although I understand that it's not possible to give everyone a view of all that is private/invisible, presumably you could do a query based on what's public and what isn't? It would have to include all public groups + all groups a member is already part of. If that list is too large, split it over several pages, and add search/filters to allow members to find those groups/forums their most interested in. Ideally, the most recently active groups would be at the top by default.
Otherwise, how are you going to combine the proposed view's front end with the corresponding groups/forums in the back end? Will the new front end link to the new groups with the same purpose, like Writing Tips & Advice or Additional Feedback, or will these be two separate repositories of similar information? I hope it's not going to duplicate functionality. That'll make the new site even more complicated, especially for those unfamiliar with the old site. They'll see two nearly identical places to post and not know which to use.
There must be something about the implementation complexity that I'm missing if you're planning on simply duplicating the old functionality side-by-side with the new group forums that already do most of what people are asking for. They just need a filtered view of all forums available to them, minus the big graphic icons that eat up valuable screen space.
And, when we're in a specific forum that we're not already part of and want to post to, an Apply button would be needed that duplicates the current Apply button function in the group view. If the group settings allow a user to immediately join the group, a single click on Apply would be all that is needed before a user could post, all without leaving the forum. If Apply requires permission, then user has to follow those steps and return later to post to the group forum once they're a member.
It seems like that would give you one back end with just two different front ends.
Thanks.
Dirk