At Force 3 the pod will always have 8 enemies. Most of the enemies are ADVENT soldiers, but you can have a Sectoid or Viper working as the pod leader.
At Force 4 the ADVENT soldiers are removed from the list. You can still have 8-man pods, but every enemy is an alien from a list that at Force 4 includes Sectoids, Vipers, Sidewinders and Faceless. MECs can be includes normally as followers to any alien that allows MEC followers. The problem appears when you roll a MEC as the pod leader because the list doesn't include any unit that can follow a MEC at low Force level. This means that, at Force 4, you can have a single MEC take the place of the entire 8-man command pod. The combination of the lack of possible followers and the limit of two MECs of each type per pod means that the MEC pod takes a very long time to reach the full 8-man size. The compositions of the MEC pod at each Force Level are:
- Force 4: 1 MEC
- Force 5-7: 2 MECs
- Force 8: 2 MECs, maybe an Archer
- Force 9: 2 MECs, 2 Archers, maybe a Heavy MEC
- Force 10-11: 2 MECs, 2 Archers, 2 Heavy MECs
- Force 12: 2 MECs, 2 Archers, 2 Heavy MECs, maybe a Longbow
- Force 13-15: 2 MECs, 2 Archers, 2 Heavy MECs, 2 Longbows (8 enemies, finally)
- Force 16-18: Superheavy MEC added to the list, pod is 8-man with max 1 Superheavy and max 2 of every other type
- Force 19-20: max number of Superheavy MECs is now 2 like all the other types
This problem also affects Troop Columns, but is less noticeable there because the pod has 6 enemies instead of 8 and is included only in some schedules, not all of them.