I designed these MEKs to make the most of our resources, so while alone they're devastating fighting machines, together they're more than the sum of their parts. I mean that literally - we have the resources to make four of them, but when they're all in close proximity, they can fuse into an an even more powerful MEK. A MegaMEK, if you will.
I got the idea when I was messing with the teleportation tech we we found on those hunter/killer robots that roam the city. Instead of physically linking the MEKs together like puzzle pieces, I combine them on the atomic level via teleportation. It's my masterpiece, the ultimate fighting machine, with the most efficient Element reactor and most powerful energy sword ever constructed. None of those monsters will stand a chance against it, no matter how big.
As long as we find some pilots that can handle it, that is.