A lot of them are Palestinian, they just work behind the scenes. Like I said, the production of weapons is mostly done by them. And even the other rebel groups have many Palestinians in them.
If you think Saudi people make them up you're wrong, yes some of the frontline fighters are saudi and other gulf arabs but the training, tactics, and weapons production isn't saudi based.
The other rebel groups don't really have any training, besides get a gun practice a few shots and go fight.
This is already acknowledged by syrians everywhere, whether they are from your local community or elsewhere. They know over 40% of the rebels are Palestinian.