You’re killin’ me… 
That would require more than one thread to have any meaningful brainstorming sessions. I will need to give it some thought before I try to tackle one of the many sub-topics that just the “main game” topic engenders. Then I will need to come up with the correct OP thread wording to create a constructive environment to solicit brainstorming ideas (versus either rants or raves regarding the current state of things), and then I will need to come up with a few ideas on the final topic itself just to kick things off. 
Arms Race and Mayhem Modifiers both seem to already be covered. I think that annointments as a topic has been beaten to death, but maybe it would be worthwhile to gather constructive ideas all in one place (assuming no one else has done so, at least recently). Technical bugs/issues are completely out of my purview (and are probably better suited for the other boards).
I suppose a reasonably easy topic might be a review of current endgame content and brainstorming ideas on how to expand/enhance/prolong the endgame experience (something a little less Viagra-ish than say, just adding OP levels and increasing level caps - not that those can’t be fun, mind you, but the limits to their staying power are well known…
). Give me a few days to think about it to see if my creative muse inspires me to anything.