Yes, we didn't see Palaven in ME1. But we knew about it. We met turians, and even those who were from Palaven, like Garrus. ANd there was the hope of seeing it in a future installment: ME2, ME3, ME4, etc.
Do you remember in the early days of ME3's hype how excited people were that we'd finally see Earth, Mars, Sur'Kesh, Rannoch, etc?
We'll still know about Palaven in ME:A - and there will be Turians on the Ark, and it's pretty easy for us to meet characters who were from Palaven or have a history there - ME:A meets all the requirements you just allowed for ME1.
If this is the argument, "well, we might see Palaven in a different game", I'm not sure that would sway Bioware on any level. If that's enough, then I propose Bioware could make Andromeda 2 - some arbitrary way down the line - which takes place far enough into the future for us to see Palaven again through regular Andromeda-Milky Way contact. And people may just as well be excited to see how Palaven changes in all that time. The point is you're employing a double standard. What you are applying to ME1 is not being applied equally to Andromeda. "We had the hope of seeing Palaven in the future" - but you didn't see it in ME1 and that was fine, ergo Andromeda will be fine without Palaven.
As I said, we visited the northern edge of Amn in the first game. In BG2 we got to see more of it, and even met a few characters mentioned but never seen in the first game.
The Northern edge of Amn is the northern edge of Amn. I believe we spend the entire game in Athkatla. Regarding the second bit, Andromeda will meet that criteria if they throw a couple cameos on the Ark.
BG2 continued to explore the implications of being the Bhaalspawn, the progeny of the dead god of murder. Heck it's the whole reason Irenicus was interested in you. None of this vague "You're a symbol" nonsense. We can only hope that "humans are special" will not be further explored in MEA
^In that case, Andromeda can function as the story exploring the implications of the displaced Council races, forced to flee their home, friends, and family, in the face of genocide for the unknown - to essentially act as the new humans in their own First Contact War, while attempting to navigate their political hurdles and exploring new planets. Actually, that sounds extremely applicable for a Mass Effect spin off, given both ME1 and ME3, and matches your Bhaalspawn comparison fairly well.
What connection does Andromeda have with Mass Effect so far? Have we met anyone from there? Did Shepard ever visit an Andromeda world? Did the Council have any economic or trade treaties with races from Andromeda that the Reaper War threatened? Has visiting Andromeda ever even been mentioned as a possibility?
Beyond the fact that we're taking the races, technology, history, political tension, with us? That we're potentially getting an "East meets West"-type setting? I'd really not like to explain what a spin off is again. Having no contact with the galaxy you're going to encounter for the first time is the entire idea behind "exploring the unknown".