They couldn't take just a single route.
I suggest that anyone that hasn't played Ever 17 not look at anything that could possibly even hint at spoilers (anyone that wants to respond should use spoiler tags as well), so...The big plot twist wouldn't work that way.
They'd have to switch between routes or something, but that would just be a jumbled mess.
Not to mention that being able to see everyone's faces would give certain details away. They could have Kaburaki get plastic surgery so that he looks exactly like Takeshi, but it would be ridiculous to have Kaburaki look exactly like Hokuto as a kid, even if they did some messing around with genes so that it worked or whatever.
Anyways, yeah, I think you can see why Ever 17 just wouldn't work as an anime.