I was wondering if anyone had any opinion on using this ruleset to run either the Dawn of Defiance campaign, or the campaign from the WotC rebellion era sourcebook. I don't know how well it would work, or if you could even make it happen. I also have the Tempest Feud campaign from WotC, but it was intended for mid level characters.

Dawn of Defiance might get tricky where Force-using enemies are concerned, particularly for Echoes of the Jedi, but other than that I could certainly see DoD being viable for EotE, provided you're willing to rebuild the various NPCs, which generally shouldn't be too difficult.

Same would generally hold true for the campaign from the OCR Rebellion Era sourcebook (I'm assuming that's the one you're referring to, as I don't recall the Saga Edition version really having much in the way of a campaign). Again, might have some rough spots where would-be Jedi are concerned, but provided that your players are on-board with not immediately being part of the Jedi Order's rebirth, you should be okay.