There must be a strong argument for saying the major development line for MMA is the japan->jitsu->judo->brazil (I think a student of Jigoro Kano took it to Brazil with him) and then the emergence of vale tudo. Muay Thai looks to me to be the major source of inspiration for strikers. What influence do you see from Bruce?
The philosophy that striking and grappling can be combined into the most effective way of fighting. Judo and Jitsu fighters do not like to strike, they do not like to stand and they do not like getting punched. This limits them in their effectiveness overall. BJJ just proved effective in early MMA BECAUSE of style limitations. When you have a group of strikers who have NEVER seen ground fighting before, then of course it will be effective. If anything, Bruce's ideas of shedding pure styles for proficiency in all aspects shows true in this.
Doesn't every style of martial art begin with a rejection of an established set of ideas and the incorporation of new ones? What made Bruce's rejection of Wing Chun and development of Jeet Kune Do unique in this regard?
But in the rejection of a style to establish a new one is a never ending cycle. You're stuck with one style no matter what. "This is not the way to strike. You should do it like this and only like this" just sets a new group of limitations on yourself. To reject somethign only to cement yourself in a new way is just counter productive. Then you establish a group of narrow minded people.
As for his methods of training - it has taken us a long time to shed the ideas we picked up in the 70s and 80s, especially the idea that bodybuilding methods are suitable for improving performance. It isn't about how you look (although it is handy if you are a movie star). How do his methods compare with the way martial artists train today?
His methods ARE the methods used today. Compare any training regimen of a top MMA or boxing star today and compare them to the ones Bruce used. The are the same principals. Weight training to increase muscular strenght and endurance, cardio work to improve heart and lungs to support the muscles, proper diet to ensure that the body can be healthy enough to train very hard.