Follow the idea of rP19095 which was reverted in rP19103 (it was not working).
The bugs are now (I hope) fixed.
So basically I could just commit again that reverted part. But while at it, ...
Sure the chariot come from nowhere, ...
It's not something which is my deep desire, so add a request and I will adress it. (Even a "no" is ok). But don't start eternal discussion.
It's mainly a diff to test bugs of the upgrade feature and see how that feature work in game.
(I don't adress file namming in that diff).
Needs D960.