Russia doesn't want Assad to go - either to Lake Geneva (some hope) or more likely the same suburb of Moscow that houses Ukrainian ex-president Yanukovych - unless they can be sure that he will leave behind a regime that is willing to allow them to keep Tartus as their Mediterranean naval base.
That is what it will come down to in the end.
There seems - in fact there is - little or no prospect of Assad and his family winning a democratic election in Syria, with or without the participation of the vastly growing Syrian diaspora. It is inconceivable that he would ever be involved in such elections, if only for practical purposes. What would work, presumably, would be a deal where Russia was persuaded that a post-Assad Syria would not be inimical to it, in which case they could take him to Moscow and a new start could be made.
Saying that there can be no solution involving Assad is not a bargaining position, it is simply a reality.