**If the gist of my post has already been stated by others previously in this thread, then please just ignore - I haven't had time to read all 26 pages, but I would like to still throw in my $0.02.**
The more I think about all the comments made so far by BW folks regarding Next Mass Effect, the more I am convinced we are going to get a continuation of the MEU we already know - the Milky Way, post-Reaper invasion, Shep & the crew existed and saved the day. I just can't see them going with a reboot, an alternate universe, a new galaxy (Ark Theory), or a pre/side-quel.
My reasoning behind this is simple - look at what BioWare has already done with their other major franchise, DA. I know the Dragon Age series and Mass Effect don't make for a true apples to apples comparison, but enough similarities exist that I think it still applies. Inquisition was not a direct sequel to the previous game in the series, but it is still built upon the world already established in the previous games. To achieve custom world starting states without being able to import saves, BioWare developed the Keep, an app that lets players tailor the starting state of their game world how ever they want in just a few easy minutes by reviewing key player choices from the previous games.
By making just a few simple assumptions about the state of the MEU - nothing more difficult to accept or "hand-wavy" than things BW & Mass Effect have already asked us to accept in the original trilogy - it would be fairly straightforward for BioWare to do to Mass Effect exactly what they have already done to Dragon Age. That being, bridge the console generation gap with a new entry in the series, one that is a continuation of the previously existing game world, but not a direct sequel. To start, just place the setting 100-150 years in the future; any more and the you would start to expect major technological advancements that would render the setting less familiar to the player. The major player choices everyone keeps yelling about, things like race-outcomes such as the Geth vs Quarians, or the genophage cure, could be reflected in NME via the same mechanic used for the VS in the original trilogy. Don't make any of the key, core NPCs one of the potentially non-existent races, and for all other less important NPCs just have an alternate-race NPC ready to fill in and deliver the dialog/quest/action in question. Even if you make a major companion/NPC from one of the potentially non-existent races, it would be easy to incorporate their absence, so to speak.
The three ending choices will be slightly harder to incorporate (in particular, synthesis) into a single world-start point, but again, I don't see it as impossible. As a quick example:
- Destroy - Reapers defeated, Shep & most of the crew are dead/gone (Krogan & Asari companions still possibly alive due to their longevity, and available for possible limited cameos), the galaxy is still wrapping up the rebuilding/repopulating efforts. In rebuilding the relays, new parts of the galaxy are opened up for exploration via the rebuilding of previously unused relays (of which there are/were many). No geth. Quarians possibly alive, but as a race/faction, not a major player. Krogan around in limited numbers, and if genophage cured, more robust numbers.
- Control - Reapers controlled, Shep compels Reapers to help rebuild, then the Reapers (and Reaper-god Shep) disappear into dark space and have not been seen/heard from again. Galaxy is still wrapping up the rebuilding/repopulating efforts. In rebuilding the relays, new parts of the galaxy are opened up for exploration via the rebuilding of previously unused relays (of which there are/were many). Geth possibly alive, but as a race/faction, not a major player. Quarians possibly alive, but as a race/faction, not a major player. Krogan around in limited numbers, and if genophage cured, more robust numbers.
- Sythensis - Reapers help rebuild, then the Reapers disappear into dark space and have not been seen/heard from again. Fundamental changes to life (organic & synthetic) from Synthesis are very subtle, and still being studied (they are little understood since, you know, everyone kind of needed to help rebuild the galaxy). Galaxy is still wrapping up the rebuilding/repopulating efforts. In rebuilding the relays, new parts of the galaxy are opened up for exploration via the rebuilding of previously unused relays (of which there are/were many). Geth possibly alive, but as a race/faction, not a major player. Quarians possibly alive, but as a race/faction, not a major player. Krogan around in limited numbers, and if genophage cured, more robust numbers.
Now those possible summaries aren't perfect, or even anywhere close. But is the hand-waving around the long term effects Synthesis (or any item, really) any worse than what ME has already asked us to accept in the original trilogy? In my opinion, no.
Wow. Sorry for the novel.