So here's a Gen1 TecSpec card, and this is where the idea comes from, I know that many of use have always looked at that and said, yep these are RPG stats, and so lets do this thing!
Primes, Stat therefore are as follows;
Then we have Megatron's:
So we have these two guys as examples, top of their game in their prime and ready to get to fighting, but what do these stats mean, how do we use them, and how do we build something off what we are seeing?
Lets define these stats....(we will use Mr. Webster's site....), I'll be pick the most suitable definition as I see it.
STRENGTH: the quality or state of being physically strong 
INTELLIGENCE: the ability to learn or understand things or to deal with new or difficult situations 
SPEED: the rate at which someone or something moves or travels 
ENDURANCE: the ability to deal with pain or suffering that continues for a long time 
RANK: a position in a society, organization, group, etc. 
COURAGE: the ability to do something that you know is difficult or dangerous 
FIREPOWER: effective power or force 
SKILL: the ability to do something that comes from training, experience, or practice 
So Strength, Intelligence, Speed and Endurance all belong together it seems as they would directly affect games play, and Rank, Courage, Firepower and Skill seem more subjective or maybe not directly affecting game play.
Lets look at our secondary abilities, Rank, Courage, Firepower and Skill...
Rank seems to be at best a type of leveling system, like Character Level, maybe....Yeah probably. It seems the best why to use this stat.
Courage is tough, I want to maybe use it like Charisma, or some kind of Luck or Effort roll of some sort, like Karma from the old FASERIP game....
Firepower, is odd, Do I use it as a literally use of Weaponry, or like some kind of damage modifier for weapon systems?
Skill, kind of locks this up for me, as I can see using skill as a modifier for skill checks and Firepower being used the same way...kinda brains and brawn types of modifiers.
So Rank will be Character level, Courage will be a general effort bonus used to overcome difficult situations, Firepower is a bonus to Combat, and Skill a bonus to Skill usage.
Our primary abilities seem to be clear enough...basically using them as most other games...so I wont go into that...
Enough for now, got some stuff to consider...