Stonebreaker - thanks for raising some good points. (Loved your sprint vs. marathon analogy!)
As for why the mods you mentioned are or aren't on the list, mostly it comes down to whether or not we've seen it done for a well documented improvement in efficiency.
Roller cams are a known efficiency improver (Honda Insight 1st gen. had them on its 1.0L motor), but I don't know anyone who's done it and documented it (sounds like you do) in their back yard. When we initially made the list, we were reluctant to include tips that were
theoretically possible, but no one had tackled.
If you can point to link-worthy examples of mods that should be on the list, please do.
On topic of bean-counting/cost effectiveness of mods, let's all remember there are multiple motivations. ....And then move on.
I personally don't do this primarily to save money (FYI, Christ: measured that way, the ForkenSwift is a
giant money hole! Even if it only cost ~$1K out of pocket). I do it because it's inherently interesting to me and an enjoyable hobby.