Just a little story idea I wanted to get out of my head.

Basically, the Protheans in this story are replaced with Alterans. Assuming that the Alterans are 'slightly' more intelligent than the depicted normal races of Mass Effect, the Alterans didn't just discover Eezo and the Mass Relays and decide to just stop innovating. End result is Stargates for instantaneous planetary travel for travel via small vehicles, while the larger ships make use of the Relays.

Then the Reapers swoop in and the Alterans flee to Andromeda and are subsequently nearly wiped out by the Wraith, thus causing them to flee back to the Milky Way where they hide from the Reapers until they leave, doing what they can to ascend, and leaving the Stargates and messages of the Reaper threat for the lower races.

The end result of this... is so complex as to be insane. Meshing the events in the timeline for the rise of the Goa'uld Empire and the rise of the Council races and determining how each event would affect the other is an entire story in and of itself.

Honestly though, I think the Goa'uld would end up taking over the Batarian Hegemony and remaking it into the Goa'uld Empire, and would probably control a significant chunk of the attican traverse. The Asari with their mental abilities would probably be naturally resistant to Goa'uld possession and thus a war between the Council races and the Goa'uld could very well result in a stalemate between the two with a cold war of sorts.

As it is though, with the Goa'uld concentrating on the Council, I don't think they'd get to exploring as much, so Ra wouldn't end up finding Earth. This means the only gate Earth would have would be the one in the Antarctic, and the world without the influence of ancient Egypt would probably be quite different. Maybe even still Roman, with no dark ages to speak of.

Going with that, the Republic of Terra would, by the time of the movie when the Egyptian Stargate was discovered, would probably have space elevators, a planetary ring, and colonies. Honestly, it's a question at this point of whether they would discover the ring in the Antarctic first, or the Prothean ruins of Mars. Possibly one after the other, or both at the same time even.

With the Terrans pushing into the greater galaxy via the Stargate, their first discovery would most likely be the same planet from the movie. As for whether it's deep in the Empire's territory, or just in the Attican Traverse doesn't matter I suppose. At this point, I foresee this story following a number of elements similar to another story where the Roman Empire didn't collapse that I read on fanfiction dot net, only when they get to Abados, instead of humans, they discover a slave camp with Asari, Turians, etc.

The story can go many ways from there. As for the Reapers? Well, the Alteran messages warning of the Reapers kinda require that pesky ancient gene to unlock their technology to read. While there are still the repositories around, and some races like the Asari were able to get a leg up by reverse engineering stuff (As well as probably impressing the Asgard or something), it takes humanity to truly unlock what's going on, and while the Council is all for this new friendly race, the fact that said race is bringing sudden tidings of doomsday where there were seemingly none before isn't exactly well liked.

Thus the Terrans probably won't become one of the member races under the council. I imagine they might take in the Quarians though and make a third party Alliance, and they might even get the Tok'ra to join them too.

As for the first contact war, the only thing close to that happening would probably be conflict with the Goa'uld Empire since they first struck out into the greater galaxy with the Stargates rather than the Mass Relays. That doesn't come until later, when the Empire shows up with some Hataks to attack the Terrans and their colonization efforts.

So... yeah. That's that idea gotten out of my head now. Finally.