*Shrugs* it's not the setting that I have an issue with, but rather the excessive interjection of politics. With that said, this will be my last word on that topic.
Anyway, I concur with your paragraph for the most part. Bruce Lee is the lifeblood of both BB and FOF and those movies would've been completely different without him. WOTD and ETD wouldn't even exist at all as both projects were his brainchild from their very inception. While having Jimmy Wang Yu star in Big Boss (or another movie extremely similar to it) would definitely be interesting, I don't think he or anyone else in HK inspires the humanity and down-to-earth charisma Bruce has.
I don't think Bruce's presence as a character (Well, with the probable exception of Chen Zhen, maybe) automatically the cycle of deaths on those 3 movies. For instance it is hinted early on in TBB that Hsiao Mi and his gang already had a habit of chopping up and concealing body parts' in ice blocks long before Cheng inadvertently provoked the discovery of their drug operation. And of course, the antagonists for FOF (Japanese army) and WOD (Italian mafia) were already engaged in spreading misery and murder long before the protagonists' came along. If anything, the involvement of Cheng Chao-An, Chen Zhen and Tang Lung in their respective movies is what brought an end to the bad forces for good, albeit at a lot of personal cost.