What elements? Chai returning? If he returned in S4 instead of S3 how would it make any difference given how little he affects the events of S3?
Again, I think you could make this argument of many of the events and elements that have taken place in the series so far. If Xiuying had shown up and given Ryo the pendant at the beginning of Shenmue 3 or had Ryo been given the poetry scroll by master Feng and told that it was one of his father's old possessions, would it really make a difference?
I'm saying that they are important, which is why you can't omit them from a proper summary the way you can Chai and the random gangs. Ryo carries Xiuying's pendant with him, that's definitely going to pay off by meeting Ziming and so, a summary of S2 that omits that is incomplete.
I certainly agree that these elements appear important, but until we reach the point in the story where they come into play, we really can't know for sure.
What if Xiuying giving the pendant to Ryo was simply a metaphor for her letting go of her brother and the guilt that she felt for not convincing him to stay? Him leaving as a child and her inability to convince him not to go is something that she's carried with her for her whole life. Ryo following the same path in spite of all of her warnings and training may have helped her to accept that sometimes, people's minds simply can't be changed and that there was nothing she could have said or done to have stopped her older brother from leaving all those years ago (especially considering that she was only a child at the time).
I really hope we meet Zimming and that the pendant has an impact on that situation, but there's no guarantee that either of these things are going to happen.
Conversely, we are given an amber pendant by Elder Yeh during Shenmue 3 and are also told by Shenhua that she had been given an amber pendant by her father when she was a child. How can you say with any surety that this pendant won't come into play somewhere later on in the story and that the pendant itself doesn't have some kind of connection to her powers?
I feel like there's a lot of overlap with the masters teaching Ryo patience...
Agreed, but I think this is emblematic of Ryo's inability to put his emotions aside and accept his own limitations as a martial artist. We see this at several points throughout the story - and that his first reaction after getting his ass kicked by Mr. Muscles mk.1 is to go straight back for a second round suggests that he still needs to learn the virtue of patience before he can progress as a martial artist.
This is possible. Another possibility is that the story was kept purposely small in scale as a way of hedging bets on the possibility of S3 being a massive success and Suzuki getting more freedom to expand in S4. Again, pure speculation.
I really don't subscribe to this idea that Yu saw Shenmue 3 as nothing more than a launchpad for Shenmue 4. Unless a deal was struck with Deep Silver to publish both Shenmue 3 and Shenmue 4 (which I suppose is possible, if not a little improbable), Yu had no reason not to put his all into Shenmue 3 and make it the best game he possibly could.