When I was developing Quincunx as an RPG, it used six elements and six types of action (where the combination of action and element determined a character's specific abilities). For the boardgame version of the game, I was going to strip the game down to 6 action types that drew on different resources at the character's disposal.
This way you'd get different types of attack styles based on different elements, different skills, etc.
But for an entry level board game, the combinations are a bit complex.
So I stripped it down to 6 actions only...then stripped it further, down to 4 actions. Attack and Defence are combined into a "combat" score. Allies was removed.
But now I'm thinking of adding "Allies" back in, or at least adding something more social back into play. I'll probably combine skills and knowledges into one category.
So we'll end up with...
Skills/Knowledges (still deciding a name for this category).
Allies/Leadership (a name needed here as well)
The four categories add enough interest to take the game beyond typical board game mechanisms (where you're often lucky to get a combat/non-combat, or a combat/magic split).
Complexity is added, based on the locations were events take place in the game and a few other factors.
For those who are interested, I hope to have a playtest version of the game available shortly.