The whole point of the creation of firearms was to kill enemies from afar before they got close enough to kill you with a melee weapon.
Given the extreme sophistication of today's and tomorrows military technology, in relation to being able to track a fast moving target, It will be hard pressed for a Mech, even if it is running, to be able to close the distance on a normal battlefield and get within melee range of any enemy opponent. Far better off sticking with conventional long range weapons.
Re: Japan Combat Mech
#41SCP:CB Administrator. 99% of my statements are my own and do not represent the official developers viewpoint.