...Making them easier to kill with a Brummbar wouldn't wreck balance or anything but I do think it would hurt the diversity of the game slightly while not really improving game play.
Imo late game stock counter's to emplacements actually increase the diversity of the game. Why should someone have to chose commanders with FMHT or other doctrinal solutions to counter emplacements? Why not make units that see little action more appealing by increase utility, doesn't that increase diversity?