Its a combat group or combat task force (mostly WWII terms IIRC), take your pick . . . and then you put the appropriate size indicator before that name. Typically Combat Groups are permanent formations while task forces are as the name indicates to carry out a task. In one of your examples you said 12 mechs and 12 BA squads- technically that is battalion strength with a mech company & 4 BA platoons, which is understrength.
If you ever read Coyle's Team Yankee the POV formation is a reinforced company sized formation, the term in use at the time for a temporary (deployed to the border w/action imminent) combined arms formation is supposed to be Team. The majority of the organization is Yankee Company with an attached mechanized infantry platoon for the purposes creating the lowest level combined arms combat unit for both defensive & offensive purposes.
So there you have three terms, no matter what you call it- be it Company Task Force, its actual strength needs to be noted even if you call it a smaller formation.