There are four distinct roles given to figures in the WRG Ancients and Medieval rules, and one more that is implied (and later incorporated explicitly into Hordes Of The Things). Since I may have some use for those in terms of characters, it seems worthwhile to classify them and discuss them briefly.
First is the obvious role, Casualty Infliction. The purpose for inflicting casualties can vary (the two main ones are to weaken opposing units and to encourage rash follow-up movement), but this is the basic function of a figure on the WRG tabletop.
Next we find Morale Adjustment. This is primarily the role of leader figures, but also standard bearers, holy figures, and magicians in the fantasy supplement.
The third role is Scouting. This is a relatively minor role in WRG, mainly used to see who is allowed to outflank whom. Still, we may find use for this role among adventurers.
The final role of those which are given WRG rules is Construction. This is a fairly broad category which includes mining and countermining, building artillery and siege equipment, destroying or repairing buildings and walls, and so forth.
The implied role is that of Infiltrator, which would include figures that are trained to scale walls, sneak through sewage openings, and the like. It could even include disguises and espionage. This isn't dealt with in the WRG Ancients and Medieval rules, but Hordes Of The Things includes the unit type "Sneakers", which is defined as:
"[I]ncluding all bands of infiltrators on foot, such as bearers of magic rings, master thieves, assassins, ninja or wraiths. They do not fight, but can penetrate or deceive enemy troops to capture a stronghold or attack a general unless precautions are taken."
In considering how to differentiate figures from one another, I should keep these roles, and the things that they imply (such as various manufacturing talents implied by the Construction role, or for that matter other non-combative functions such as artistic endeavors), in mind. Perhaps, inspired by the five levels of training defined by the fighting classes (General, A, B, C, D), I will decide on giving each category a rating (perhaps Superior, Elite, Expert, Trained, and Untrained), allowing each character to select such ratings within limits defined by the rules. One possibility is to allow each figure four total increases to spread among the five roles (though perhaps the Construction role will be further split into various particular roles, so that a Master Carpenter is not also a Master Smith and a Master Harpist; certainly, the Morale Adjustment role will be subdivided, at the very least into Leader, Religious, and Magician, and probably further than that), with each increase giving some ability in that role. This will allow players to define their own "character classes", as it were, by giving them the ability to select what particular mix of abilities they want their figure to have. Character advancement (remember the note on "heroic attributes" from the Fantasy Adaptions section) would then improve the figure's facility with those abilities.