Siege Rework
I really don't think Siege Units are where they need to be.
With siege, cities fall (at the correct rate), but without them they often feel invincible. Sadly until Field Gun many cities just cannot be sieged due to terrain blocking, or at least can only be hit from limit spots that you can't even get a siege unit to in the first place.
But then, if you get Range, all issues are solved. So it becomes a case of whether or not your neighbour is positioned in such a way that you can come away with 3 range Trebs to fight a real war later on. There wasn't really anything you could do about that. This is no fun.
The worst part of all this is that it is completely beyond the AI planning.
There's a similar problem in the Field line where what you really want is Splash+Logistics. Most of the game you can't get highly promoted siege because its rare they get to attack (and they die if they try to defend). This means they feels borderline useless against land units, and might as well just build more archers.
Here I've tried to alleviate these concerns whilst still allowing for powerful promoted siege units. The most significant change, Indirect Fire for all Siege Units, is particularly significant because of how it helps out the AI with early war.
Thanks to FlamingCheesePie for discussion on this:
Note: I also tried making Range baseline instead. It's quite game-warping and results in lots of hits from the fog and high death rates (not unhealthy but can feel unfun), so I opted for Indirect Fire.