Hello,
What would you all think if in the loading screen before the match starts, all players declared their intentions on which direction they will move. Then the game can warn about a flank falling short of what would be normally viable.
Sadly it's in the first 15 seconds that a "lemming train" forms, and it is very hard to make players aware of it during that time, and to have someone take it upon themselves to halt and divert. Also, that map that I saw where the game suggests which positions are ideal for which class for a map, that could be used to help players make their lane choice.
This would of course all be non-binding, and people can still do a lemming train, but I imagine that it's often just this inertia in changing one's mind after the start of movement that causes most of them, and not malice or intention to lose a match.