The real problem, if it's a sequel, is that people expect the decisions of Shepard to be there. I'm not talking about the minutiae, I'm talking about the big things that affect everyone in the galaxy, like curing the Genophage. Either they declare one version of the events as canon, they set it so far in the future that handwaving different pasts becomes possible or they do a pre-/side-quel. Or it's Mass Effect: Space Ark.
Right, which is why I'm saying anybody expecting/desiring both a) a sequel and b ) said sequel to take into account your trilogy decisions in a serious/satisfying way are setting an impossible standard and doomed to disappointment. Hence why some people eager for a direct sequel (like myself) are quite open to the idea of picking/constructing an ending state and moving forward instead of dancing around ambiguity or trying to accommodate saves. It's also, as a personal belief, why I get a little bit frustrated (even if I am empathetic) with those who want their choices to be taken into consideration, as if being a sequel automatically constitutes as "sequel to your Shepard's trilogy". Fans have a tendency to obsess over the canon when the series as a whole has a pretty malleable and subjective canon. Hell, there isn't even a canon to the entire trilogy's story. Fans have attached themselves to their canon, but their canon is no more justified, truthful, legitimate, or important than any other fan. There literally isn't a canon for the Mass Effect trilogy.
Personally I believe the concept of a sequel (ideally) constructing a new ending, one that takes bits and pieces of all three while introducing new ideas, and moving forward with that isn't forcing a canon or disrupting a canon because to do that is to imply it's a sequel to your trilogy or my trilogy which, as established, has no canon. It's a bit of a paradox to accept the future of Mass Effect is in no way related to the Shepard trilogy in narrative/content then in the same breath expect it to be a direct sequel to your universe. A constructed ending, bits and pieces, isn't a sequel to anyones universe. An impossible universe state from the trilogy. But why not? I can appreciate people disliking this, but again I don't feel it's entirely warranted if a sequel isn't specifically marketed as a sequel to your universe. It doesn't conflict with the canon because it doesn't attempt to change what I did in my Shepard trilogy and how my Shepard trilogy ends. And since it's an impossible ending, no one group of fans has their ending pandered to at the expense of others, nor does they attempt a universal retcon of the ending that is applicable to all universes. My experience in my Shepard universe still exists, hasn't been retconned. It just isn't relevant to this (hypothetical) sequel. And that's okay, because it's also not trying to be about my Shepard at all, nor is it about anybody else's Shepard.
Honestly I think the "set far into the future where all endings converge" idea is worse, as it attempts to take my content, recognise it, acknowledge it, then deliberately skewer it to whatever the writers feel is appropriate, negating all my decision making along with the decision making of every other fan. It bottlenecks all the variations. Alternatively, constructing a new ending and making that a template for a new series does the opposite; it does not bottleneck the ending variations, but accepts a singular variation and just uses it as a template. If that variation happens to be a literal ending state from the trilogy, that's bad as a specific group of fans are appeased while others are not. If it's a new ending, bits and pieces, then nobody has their personal Shepard universe disrupted.
Wall-o-text coming to an end in a topic that I've severely derailed (my apologies), but I guess I'd summarise it as this: there are many Mass Effect universes, all equal, non greater. In my universe the Genophage was cured, Wrex at the helm of what will hopefully be an age of enlightenment for the Krogan, and the Quarians and Geth found peace. That is my Shepard, my adventure, my universe. Yet in other universes the Genophage remained intact, Wrex died years earler, and the Krogan are decimated. The Quarians were obliterated by the Geth. It's not my universe. But it is a universe, one I must recognise as just as valid and important as my own. If I am told I am getting a sequel to my universe, I would naturally be upset if my decisions are made irrelevant. As would anybody in the latter scenario getting a sequel to their equally valid universe. But with a palette of so many possible universes, is it no okay for a "sequel" to take place in one of these universes even if not your own? If explicitly stated as not a sequel to your universe, or my universe, or the poster above me's universe, or even anybody at BioWare's universe? A new universe, one of many, that does not invalidate your own, that has its own criteria, its own adventures, and even its own Shepard owned by nobody.
In a universe of many possibilities, here is one.
That is what I hope.