Interesting options, my opinion was that they would use some of the simpler and faster machines- since they are unlikely to face a 3/5 assault unit, or as much heavily dug in opposition they could not roll over it.
I planned a four mech lance company, standard armor company, and a IS Std BA company to create a combined arms battalion. So everything is going to be 4/6 at the slowest so they should be able to keep up or catch some of the older SMM equipment and whatever dregs local nobles fielded. The armor company's lances may be split between the more advanced & more simple models- so instead of 4 Patton (Ultra) perhaps just 2 and the other 2 would be 3025 models dug up. But since I am not sure they are still making that 3025 model, it might just be the Ultras. Such a company would, IMO, be decisive for what we see the different Chaos March factions fielding.
Mech Company
Command Lance
Zeus 9S2
Zeus 9S
Archer 5S
Axman 1N
Assault Lance
Berserker A3
Axman 3S
Hatchetman 5S
Hatchetman 5S
Support Lance
Salamander 5S
Archer 5S
Axman 2N
Griffin 1DS
Scout Lance
Griffin 1DS
Valkyrie
Battle Hawk K305
Wasp 1S
Strike Lance
Nightsky 4S
Nightsky 5T
Nightsky 4T
Uziel 3S
Armor company
Manticore x4
Patton (Ultra) x4
Rommel (Gauss) x4
BA company
10 Squads IS Std BA
It does make me wonder if DefHes put such a group into the Chaos March, would Earthwerks, Irian or Star Corps send their own representative unit?