Yes, technically that's a good idea. I don't think the time is mature for a conference. You're absolutely right.
My only advice would be to try to deal as much as possible with the people on the ground. Exiled groups, I remember, quickly develop an agenda of their own, and it's very difficult and murky then to try to establish what exactly they control on the ground in Iraq, particularly in areas that are controlled by the Islamic State. So as much as possible, you have to work with the people on the ground.
I remember, before the fall of Saddam Hussein, these people in Oxford claimed to represent the true Iraqi opposition in exile and so on and so forth, assuring us that in the event of a regime change, they would have everything under control. They said that they were very much in charge of many opposition groups, and then look at what happened right afterward.
It's a worthy effort. It's the right thing to do, but always be very skeptical and realistic about exiled groups who do not interact directly with the people who are on the ground.