Assad should agree to put the Syrian Democratic Council's ideas to a national referendum on a new constitution for Syria. The Council should accept that arrangement.
There's no reason that the democratic socialists shouldn't have full recognition. At the same time, those who claim to be democratic socialists need to understand that democratic means the People being able to vote things up or down and that, that means that one-party rule (dictatorship) over any area would not be acceptable.
By the way, if Assad were to do this and the SDC to agree, Syria would be vastly stronger than it has ever been during the "modern" era. It would be the best democracy in the Middle East without doubt.