I'm with jeanne on her suggestion - female submissives only - give an area to each if you can and think it would grow but when you mix up submissives with switches, I think it detracts from the subs being confident enough to voice the really deep things they want to with other subs.
I also think it would be unfair to other Dommes if switches are allowed private access to subs that the Dommes aren't. Hard call I suppose.
I think Oz, that they would find that what a submissive is scared to post in public, she would in private and then build the courage to bring it to the entire forum. I have seen this work successfully before.
It would also provide an area of no b/s or power tripping and especially with delia in the lead.
Solid idea delia, good luck with the endeavour!