Hrm. That last one might work well.
The renewed/enhanced Goa'uld threat is a host of new advanced
human planets, and if a variety of system lords used the time-compression technique, it even reintroduces the dysfunctional-family version of system lords.
Each new system lord would have to come up with their own ways to trick entire planets of non-Jaffa, fairly non-religious humans to do their bidding, and knowing the Goa'uld, a lot of these methods would come from human history.
Their dilemma is a bit like the Soviet one. To out-innovate and out-produce the West, they needed to become like the West, but they couldn't remain Soviet and do that. Similarly, in their utter defeat the Goa'uld saw that their old way of ruling humans couldn't compete with us, so the old paradigm (playing God to a bunch of mindless, enslaved followers) had to be discarded.
So we get Nazi Goa'uld, vampire Goa'uld, Soviet Goa'uld, warrior-diplomat Goa'uld, capitalist Goa'uld, and "enlightened" Goa'uld (Tok'ra with a twist). We also get planets where the Goa'uld overlord lost control and was cast down, leaving the humans with the remnants of whatever belief system the Goa'uld had been playing with.
We wouldn't have noticed what had been happening with new Goa'uld threat because even Tok'ra tracking devices would fail to compensate for the immense time-compression effect the Goa'uld were using, so we get caught unaware. If the story arc peters out, the teams can notice the holes in shipping routes and gate locations that lead us to the discovery of the ecosystems, or we learn of their existence from some of the advanced Goa'uld or humans.
It's a cleaner relaunch with a more familiar premise, but the Goa'uld worlds are more like ours.
I suppose step one or two for the SGC is to combine Asgard time-compression technology with the Ancient weapon on Dokara to destroy the time-fields and keep the Goa'uld planets from advancing even further.
ETA: And of course a few of the Goa'uld worlds are Cargate, the exact percentage depending on the dudes in accounting.