Not being a politician, marketer, or event planner, I can't help with planning a huge thing like this. But this suggestion is on the right track, I do believe. We will need monitors to make sure neither group gets confrontational or US/THEM when this thing finally happens.
Also, I'm thinking even more important than the official, formal "summit" with media coverage and official speakers, will be - if we can arrange this one - informal meetings of one to one, from both "sides" over lunch, coffee, breakfast, dinner breaks. Letting each "side" meet and connect to what is compassionate and caring and authentic in the other "side" - that will, at least (and this is a HUGE breakthrough if it happens) dilute the perception that all of us are falling into that the "other side" is all full of malice and negative intent - at least, I think both "sides" of us fall into that trap. The polarization and the blaming needs to start stopping.
The breakthrough cathartic moments are almost always at unplanned moments, which is why I can't stress enough that we should have informal one on ones with these folk. Maybe not even talking about sexuality - taking a break from all this. . .circus. Then getting back to solving the *real* problems gays and ex-gays face, as allies instead of waging combat against each other.
Am I being Utopian suddenly? Somebody smack me with a frying pan.