Abilities: What to use for derived statistics?

Now that I've thought some about what I think ability scores should look like, its time to generate derived statistics.

I have four thoughts on this already.
4+/-MOD: This creates a nice spread of possible results from 1 to 7 (rule of 7, baby) which works great for things like ENC. Good for either Allowable Choices (such as what kind of gear to pack) or for Operational Endurance (such as healing surges).
1+/-MOD: This creates a spread from 0 to 4 (most likely 1 to 3) that is appropriate either for Really Big Effects (the Rule of 3 -- if you can do it more than three times, its not cool anymore). It also means that folks who have a score below 9 (i.e., they are below average) can't attempt it at all because they have 0. I think this might be good for things that have a sub-system tied to them, because that way, if you dump it, you're basically saying, "I don't want to have to deal with this sub-system at all, except maybe at higher levels." Its also good for things you want to de-emphasize (for example, if you don't like henchmen, then use 1+/-MOD). Hrm -- sounds like a good candidate for magic (Rule of 3 + subsystem). Also good for Allowable Choices or perhaps Operational Endurance.
Primary Ability: I've already mentioned that Quantitative Effectiveness (odds of success) should be based on what your Primary Abilities are, not your exact scores.
Ability Tracks: In addition, I've thought about taking derived statistics one further. You may recall my Ability Tracks (Body/Agility/Heart -- range from +2 to -3, with 0 being the baseline; replaces status conditions). Each Primary Ability in a pair can move you up one step on the track. So, a STR/CON primary ability character would be BODY +2, AGILITY +0, HEART +0. A STR/INT primary would be BODY +1, AGILITY +1, HEART +0. This is good for things that should be generalized or could involve an interaction of multiple ability scores. For example, resisting physical damage could be tied to BODY, making STR/CON prime folks best at it, STR or CON prime folks decent, and folks with neither STR nor CON prime kind of suck at taking hits.

I've also started to divvy up the ability scores.

CON / INT / WIS - I think of these as defining sub-systems or classes. CON for the burly types that take hits all day, INT for the magic-ky types, and WIS for the divine types. So, it might make sense to use these either for Operational Endurance (4+/-MOD) 0r Sub-System Access (1+/-MOD).
STR / DEX / CHA - These seem to work better for effecting choices allowed. Higher STR = higher ENC limits = more choices for arms & armor. Higher CHA = more henchmen = more choices for whom to hire in your entourage.