1) which size will beneifeit which class the best?
2) Now that we've had much more time to think about it, what class and size are you ACTUALLY gonna run through the game first with?
3) Do you think that games such as battlefield and Call of Duty will try to rip off of Brink's Free running for their next enstalments?
Don't think size will benefit class all that much. I am of the belief that Size is what makes the character in Brink. It is the major factor that defines how you play because it defines your movement, HP, and Weapon Choice. Classes have enough difference in their own abilities that you can have two "soldiers" that are completely different if you so choose.
I believe the Op abilities will benefit Lights more, and that the other three could greatly benefit the Heavies, but see possibilities at all sizes.
If my friends don't get Brink I'll be starting with a Light Soldier, if they do it will depend on what they choose.
Doubt that free running will find it's way into CoD or BF, although the concept of SMART allowing an easier way of traversing objects that a normal soldier could will likely become a popular trend.