LemonHaze already answered your question. Almost anything can be done if someone programs it, with varying difficulty.
You are less likely to find people willing to do things for you than you are to find people who can came up with thousands of ideas that no one wants to work on. Logic modifications to games like some things you've described that change actual functionality are very rare. Some things like "Stay out past 11pm" fall under the domain of cheat codes and have been done for the original games back on Dreamcast. Just look at other popular games for examples of this - mods that change individual objects / characters / graphics are very common because they are easy to do. We already have mods for Shenmue I, II, and III that change textures and characters. Mods that make more drastic changes are very rare and are often in development for many years.
Outside of what LemonHaze is already working on and some of the work-in-progress texture mods, I don't expect anyone to do many of the things you've suggested. There's a very limited cross section of users who are both capable of doing these things, have time for it, and would want to do them for Shenmue.
If you want ideas like that, I would first suggest learning how to write an Unreal Engine game. Once you know how to write games in Unreal Engine, the SDK that LemonHaze linked will allow you to change the majority of Shenmue 3's game logic.