I have two Campaigns listed under "Single Player -> New Campaign":
Demo Campaign - new maps
Tutorial
Version: 0.28.0 (Boiorix), a2cae, Win64
There is some kind of tool tip that could be changed towards your approach - but I'm against it. Everyone can understand what's up after following the above mentioned path and see the two Campaigns.
If you get neutral with an AI competitor, send traders to their markets. After that, many offer an alliance proactively after some time or if you offer one to them they agree (or still want some tribute).
Those things don't have to be related, since one doesn't even have to move the XP slider if one doesn't want to, and just use some default. Exactly the same as what happens with batch training size, there's a default in Game Options, but it can be modified in-game, which can have its uses. It's only adding the possibility to do what I previously described.
Same as above. By "replace" I mean enhance, not remove. The wounded unit health in Game Options would be the default, which one could modify in-game if wanted, since one might want to control what amount of units to actually select, and not so much what % of HP should they have (which could be useless in certain situations). Nothing is being removed.