Anyway, yeah, the FCW was:
1)With the Turians
2)Actually rather small for the Turians. It was large for Humanity because they've never faced a threat like the Turians before, so something could be done, but considering its relatively tiny scale, I wouldn't enjoy it except as a more flashback (through whatever means) section of another kind of game
3)The Asari/Council stepped in and basically held the Turians' hands back before they initiated the nuclear option to wreck Humanity easily
Interesting concepts they could play with. Lots of new and even important details we could learn (see: TIM's backstory). But a whole game? Eh... I'd rather not.
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After the FCW, the primary threat to Humanity was the Batarians. But even then, it was a handful of conflicts and then just simmering tensions (giving Alliance a public reason to always keep their defenses up, regardless of co-operation with the Turians and Citadel Council). It's another case where a whole game just doesn't seem to make sense.
Keep in mind that by 'whole game', I mean a main franchise title for next-gen systems. If Bioware wants to release mobile/iOS games like ME:Infiltrator, or more sidelined DLC games, have at it! But the main franchise doesn't seem appropriate for, well, any of the recorded conflict periods.
What Bioware COULD do is have a side adventure happening, even more secretly than anything we've known of, that isn't related to the Shepard Trilogy events but will have effects on future games/plots down the line.
A very small example is some of DAII. In DA:O, you go to Lothering and then hear it was wrecked after a short while, but move on to the rest of your journey. But in DA2, you start off outside Lothering, which is being destroyed. The paths somewhat intersect, but the plots are largely unrelated.