**Edit: My 100th, and I missed it**Thanks to the author of Beacon, Todd's response here, got me over the mental block I was having. Now I didn't take the suggestion as is, but the result is worth thinking about. The question I have to answer is, "Do the changes that I would make add to the game, based on my design goal, or detract from it?" Answer, "I don't know yet."
I am fairly certain that converting to Fortitude, Will, and Reaction is a solid decision. The vernacular is familiar enough to the 'old hands' that I don't feel it would be distracting, and might as I suggested, add to the feel I am going for. A fair tradeoff, if not a slight advantage for making the change.
But what about 'Comprehension'? Comprehension: 'capacity of the mind to perceive and understand; power to grasp ideas; ability to know'. Or in my laymen's terms, 'speed of mentally processing stimulus.' I like the symmetry. You have the toughness and speed of both the body and the mind in four stats. Combining each individually with a M20 skill results in a large pool of Saving Throw options.
My concerns are that a) it might alienate conventional D&D players by going too far afield, and b) comprehension is not 'commonly' used enough to be understood in this context.
In retrospect, I used Charisma primarily as the strength of the Mind stat, when I used it. But 'Will' is more fitting. So, in this, perhaps what Todd said is correct, "As a proponent of Charisma I would convert it to Will and come up with something else for the MIND stat (or just go fortitude, reflex, Mind and Will.)" This is how I had used Charisma in the past, but my OCD will not release the symmetrical beauty of the option discussed earlier in this post...
Okay, maybe it has not solidified, but I am vigorously mixing it around in my melon! Come on Jello!!!
Question? What question?