Since your in JKD maybe you should look at the founder. Bruce always tried to get bigger. He believed that he would be at his supreme power if he could get his weight up to 180 lbs. Simple physics says that mass time velocity equals force. The bigger you are, the harder you will probably hit.
Well, Bruce is probably an exception either way (to everything)
but I can only reiterate what the guys in my place say, and that is that Bruce got up to 160lbs and did not like the loss of speed he encountered and dropped his weight back to down to his comfortable 130lbs. (of course maybe that's just Bruce individually)
While I agree, a bigger guy can probably throw a harder punch, you must realize something about power from the muscles. (If I knew the correct terminology I would use it) but learning the correct form then teaching your muscles to connect this properly to the brain is the key. You could call it muscle memory in it, but there is more to it. It's teaching the muscle how to function into a punch properly (along with the whole body) As we all know, it can take a very long time to actually master the straight blast.
This might be a personal belief, but I am highly confident someone who masters a straight blast no matter his size will throw it a lot harder than someone who is naturally big. Where I am going with this is, certain exercises can help your body program the muscles into these movements better than others. Any exercises that would involve core movements and balance I would imagine would fall into this.
But I know from fighting methods, it mentions that in boxing, the "less muscular" can be seen throwing a harder punch than the other guy.
Either way though, the necessity of size in a fight could go on forever. The only few examples I could offer is, in the early UFC's there were no rules. And large guys did
not dominate the sport then. Also, if you notice, all the martial artists in these asian countries are very tiny yet skilled fighters. (this could be due to there diets yes, but I'm sure if they thought being larger was truely an advantage, it would change)
(I am only trying to repeat what was said to me, of course it's not going to be a 100% complete translation)
Overall I think size:
-can be intimidating (and a loss of confidence is a huge disadvantage)
-as long as a person knows how to adapt to a larger fighter, I think the advantage no longer exists)
-Depending on your art, JKD, kali, and silat do not stress strength in any of the exercises. it's all about applying little force to achieve results
(the exception being punching/kicking which as I said, I would not contribute a high bench press into the ability to mechanically throw a proper straight blast or cross)