My mercs are designed around combined arms, with the mech companies (and even lances) splitting off on missions to be supported by armor, BA and infantry. In time they will also have VTOL and ASF support provided they do not get mashed as the Jihad breaks out.
Your combined arms company's TO&E will depend on what tasking you have for them . . . for instance, I had a scenario where I had to send out rescue detachment for a group of rebels that were found by some semi-independent pirates on the world. The rebel's base was crushed, and the largest group of survivors, equipment and supplies were being hunted by a force that was overtaking them and had heavier firepower.
I HAD to send my fastest units to the site so the rebels (aka the mission) could make it to our perimeter to regroup. As it was broken terrain I was using hover tanks to cruise in, 5/8/5 or 7/11 mediums, a VTOL to drop BA, and 2 APCs with the hover tanks carrying the other 2 BA squads.
The detachment was . . . 2 WVR-8K, UZL-2S, NGS-4S, J Edgar Hovertank, Condor (Laser), 2 modified Blizzards (created before the Blacks came out, but similiar), Karnov (Upgrade) w/BA, 2 Blizzard APCs w/BA. Managed to skirmish the pirates and knock out their leader on a lucky opening salvo when the mech lance arrived. The mech lance fell back to the position the BA had formed behind a hill with hovercraft zooming about in a clear area. The pirates pushed a bit forward from the knocked down leader, got chewed and failed a morale roll. Half the light and medium mechs they had fell in their retreat. The rebels had damage to their light armor and a Vedette was immobilized at the defense line.
Similarly, I have had heavy detachments engage in ambushes of convoys. Schrekk and Alacorn roll over a hill to form the anvil supported by infantry and BA. Then jumping heavy and assault mechs clear forests and hills to land on the flanks of the convoy, neatly encircling the convoy. None of the supply trucks broke containment, and only a few lights and mediums made it out.