The Marians have some other teammates that would work well with the Thanatos, except for using units that have a C3 Master, which I haven't been able to find in their unit list for the Dark Ages. The 7SE, 10E, and 9M Thunderbolts are all 4/6/4 or 5/8/x, the aforementioned Hercules, plus you also have the Tempest 3M and the Ostroc 2Cb. That's a lot of jump capable or 5/8 heavies covering a nice mix of weapon types, and I can see the Thanatos as a lance or company command unit in that make up, or as a carrier for Marauder battle armor since they have magnetic clamps.