/SNIP
But as I've said before, making choices "resonate" across games is overrated. I would have thought the Mass Effect trilogy would have made that abundantly clear.
I am not sure if i agree with this premiss entirely. I do think that Mass effect showed that multiple choices don't "resonate" across games because they create too many divergent paths that are honestly impossible to account for that don't all seem to lead to a situation where if feels like your choice didn't matter because someone has to take all these divergent results from multiple choices over multiple games and write something coherent.
I think Mass Effect showed us that if they took 1 major choice and focused on just that as the choice that carries over they would have had a better result both in terms of players feeling like choice matters at least on the big things and been able to deliver on differences making life easier on the dev team. Take two choices from Me1 and how I think they should have been handled.
Rachni Queen & the council
The Rachni queen should have been a choice that had little to no consequences for the player because if it honestly had real consequences it would have eliminated an entire story arc in Me3 and significantly reduce enemy reaper ground troop diversity. So play things out like they actually did in the series. We get the content needed to tell the stories and the diversity of enemies to fight.
To save or not save the council, this should have been the one event in ME1 that they carried over and it SHOULD have created an honest difference in the citadel. Save the council and add a FEW humans to C-Sec but keep it mainly under Turian control but have people view humans (for the most part) in a really positive light, 'Saviours of the citadel.' In other words C-sec looks and feels like it did in ME1, alien dominated, but instead change the Turian attitude from distrustful of humans to humans are gggggreat.
Let the council die? Do the changes we saw in Me2 to the citadel, C-Sec dominated by humans, but make humanity actually mistrusted and viewed in a negative light. Present situation as we saw things in Me2, if you are mainly paragon but let the council die then give us the paragon citadel for me2, Mainly renegade and let the council die give us the renegade version of the citadel. The key is the player sees and feels an honest difference to the citadel, I honestly felt that there was very little difference in ME2 between saving or letting the council die because there was honestly very little difference. So it felt like a hollow carry over.
I think it is possible to give SOME choices real resonance between games IF they limit what is carried over and honestly make a difference to the consequences of the choice that IS carried over. When you have so many little choices that carry over and have to mention or account for all these changes you get pretty generic and minimal changes that the player will experience because there is so much work. Limit the changes to just ONE big choice and you can take the time to make that choice feel like there is real impact behind it. Over a trilogy you limit the variance to just 4, two results for the first game and two results from the second game. making 4 variants of consequences for the third game to wrap up the story arc keeps it manageable and makes the player feel like there was real honest to god impact on the game due to their choices.
TL;DR; Less is more. limiting the carry over to one choice each game actually creates a far greater impact on the game then dozens of choices that can only have a surface difference because it cost too much in time and money to make every choice feel impactful.