This is not a suggestion for Reforger (implementing it would break a lot of existing things), but for future titles like Arma 4.

The AI group entity has an array for characters (unit prefab slots), currently it is simply an array of resource names.
This makes character adjustments on the group level very hard, as the characters fundamentally cannot have any additional options, which currently are only possible via annoying workarounds:

• Group level randomization, which can currently only be done via the EditableCharacterComponent on a character level
• Things like explicitly defining fireteams (not relevant for vanilla Reforger but in modded context, it is - you have to add a parallel array as a workaround)
• Doing certain post spawn processing to the character
• Really, adding any kind of character data that is specific to a certain group, and not universally applicable to the character

Creating a container class for character resource names would significantly expand moddability by allowing modders to add new attributes to the class, or even creating their own inheriting classes with special behavior (e. g. randomized picking, or overriding character names in a group context) that can also be added to the array.