Which won't happen if you have an Islamist government. You don't have to emphasize the secularism, you just need to do it. "Soft secularism", as it were.
Even soft secularism that does not pay lip service to Islam will be seen as hard secularism. If the FSA become top dog again and are more respected than they currently are (al-Nusra in contrast seem like brave, intelligent fighters with a clear plan to a lot of rebels) then they could afford to be "soft secularists". Lip service is necessary, the degree to which remains to be seen i.e. if al-Nusra do something really silly like gas civilians then there won't be as much of a contest between the two groups.
I really don't want to get into bigoted conventional wisdom like the foxhole thing, but suffice it to say what the people truly desire is to avoid suffering.
I merely wanted to show that people have a tendency to flock to clear, simple ideas, put forth by strong leaders in times of crisis. Religion, specifically radical Islam, is playing that role in Syria, just as Communism once played in many world conflicts.
The FSA can do that. They can provide security and supplies without even bringing religion into it, and that will degrade the radicalization, especially once they inevitably end up fighting al-Nusra. As I have said before, acting rationally has a habit of making Islamist groups self-destruct.
But in order for the FSA to provide security and supplies "without bringing religion into it" (as if that's a problem for most Syrians with rebel sympathies) on the scale that is necessary, they need a lot more support than we're currently giving them. Until then the FSA are watching as their fighters and supporters are defecting in growing numbers to Islamist groups, unable to do anything about it. Maybe when the war is over and the FSA are hopefully successful people will want stability and an end to suffering, but I fear the effects of prolonged exposure to the kind of doctrines al-Nusra are espousing.