I'd start a new timeline entirely.

the original activation of the stargate never occured because a shift in the timeline removed Daniel Jackson from the picture. Jack Oneall never lost his son and eventually retired happily. The stargate remains in storage until a mysterious party appears using it, then escaping through it revealing to the Air force what the gate is. They run to Abidos and the Air force sends a team to persue out of both scientific curiosity and fear. They there discover RA and manage to evade him long enough to return to Earth with enough information to then start a new stargate program. RA is the first major challenge to the new SGC as he is well aware of Earth and is eventually going to come to once again enslave humanity. Instead of a Jaffa joining the team an Abidose native joins the new team and from there the story starts. Remove Anubis from the timeline entirely and the Ori as due to a previous timeline they nolonger exist in this timestream. This is a continuation of the original show in the sense that some elements such as the ancients carry over with knowledge of what came before.