I must say, I really like some of those ideas.
I am bad at inventing new adversaries, but maybe in the first "season" of the adventure, I could pull up an existing race that gets negligible screentime as it is; the Aschen.
Alternately, I could bring out the classic Replicators. Annoying little bastards. Chances are though that the Replicators would be impossible for players to kill that early in the adventure, regardless of how they came back into being.
If anyone else has ideas for adversaries, I am eager to hear them. I think we have established it will take place after the shows, but thousands of years is definitely too big of a leap for my tastes.
And possibly, by the power of transgalactic bridges constructed by the Tau'ri, exactly which galaxy will likely become irrelevant (it might take place anywhere from a few months after Stargate Universe, to a few decades after SG-1, but no more than a century)
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I can't help but imagine the latest SG team being an Oracle, an Alchemist, a Bard and a Paladin/Gunslinger.
Oh, and one piece of technology that I will not allow? Zat guns, or at least not the 1-shot-stuns, 2-shots-kills variety... And DEFINITELY NOT the 3-shots-disintegrates variety.