You weren't a real gapper in 2013-2015 if u didn't have a min 14 ML rush bo. You weren't getting the bricks/percies out to stop it, that was the whole strength of it.
Actually that was just generally what the ML was for in any situation. I realize I already did this but let's break it down again because it seems you forgot.
Pre-2018 T4 Gameplay:
Fatty - Use it to force people to walk into your percy/parashield legion.
ML - You rush it as an attempt to end the game before T3 numbers rise to more than a handful and enemy ACU isn't rambo.
Mega - Viable reaction to percy spam, but will lose to percy + fatty + para mix
GC - Only Aeon option against percy/brick (still not as good as those two in mass equivalent numbers)
Chicken - Only Seraphim option against percy/brick (still not as good as those two in mass equivalent numbers)
The only time you would make it for ANOTHER reason is that you just won some major t3 land pile in reclaim and want to convert it into a unit within the next 30 seconds.