My main mech gets me in rank 2, and bottom rank 1.
I am mainly concerned with building my main mech. My second mech used to be a campaign mech, until my main could deal enough damage so a heat mech is not needed. My 3rd mech is just for fun.
Mech slots 4 and 5 is for storage (including my old legacy mech) and mech slot 6 got destroyed when the first lockdown hit.
Not all my mechs are good. Only my main one is.
It would not be very fun for me if I only have one mech. I sometimes make builds for the fun/challenge. I'd sometimes head to global have fun with battles. It feels nice to see an experimental build work.