In MW4, MRM's were < 400m range weapons with higher heat and tonnage than SRM's and lower damage per missile (requiring more ammo). They came in sizes of MRM10, -20, -30, and -40 (with 40 being around 11 tons, if I remember correctly). An MRM10 or MRM20 could easily supplement most SRM or LRM boats for those instances when the target is dancing just on the edge of max. or min. range, or when there is not enough time for LRM's to lock target at 400m before the enemy ducks behind the next hill. Also, MRM's had a slower rate of fire than SRM's.
I believe MRM's would also be useful for mechs with one missile harpoint, when an SRM6 is a little ridiculous (i.e.: Zeus 6S and 9S... I think those are the two), or when an LRM system is contrary to the mech's arsenal (i.e.: Centurion... I know it's not the best example).
Is this something that players would like to see? If you're a missile-based player (i.e.: SRM or LRM boater) please speak up!
*Edit*
I add the "implemented" question and edited previous questions to better reflect diverse answers.
Edited by BerserX, 01 May 2015 - 05:00 PM.