You don’t want to fork. You could create a plugin that would remove whatever features you want to remove.
As you point out, many of those things that are tracked are tracked to improve the quality of conversation and fight spam. I guess you’re asking to disable the automatic trust level system, for starters. If your users want to be part of a system where a spammer has the same rights and privileges as a longstanding member, that is certainly possible.
If you wanted to do that, you’d start by making a list of the things that are tracked that or your constituency think are problematic and override the classes that create and depend on them.