I'd better ask right away about the biggest nightmare.
Will plugin support remain?

This option (like battles with neutrals) is practically not used anywhere. It can even be removed altogether.

In HL+U, by default, there are 2 damage dealers. And in some cases, less than 1 damage dealer.

The final version looks great. I also suggest adding an option: "Exclude Heroes". Implementation options:
1) a button that opens a window with all the castles; when you click on each castle, a window with heroes appears (like when choosing a hero); when you click on each hero, it is marked with an X (like when generating a pair of random cities).
2) just a list (third column) with the most popular hero options for banning (Kyrre, Dessa, Gunnar, Luna, Galtran, Tant, maybe someone else)

Another idea (more like a suggestion). A menu for excluding secondary skills. (Eagle Eye, Navigation, Necromancy, Diplomacy, etc.) If a hero has this skill, either the hero is blocked, or the skill is replaced with a random one from the unbanned ones.

Added 32 seconds ago

I will take the suggestions into account.
In general, it will not be possible to make everything perfect right away. So, what I release in the near future will still be refined.

Added 4 hours 26 minutes ago
Okay. I don't know how it is in 1.40. (I think not everything is smooth, as in 1.38+)
But I currently have a dilemma with the Tower reconstruction: how to implement it.

In all cities, all spells of all levels are generated at the start and cannot be changed without reconstruction.

So, during reconstruction, for simplicity, let's say level 4.
specifically in the Tower with an UNBUILT library, we can do it in different ways.

Option 1. Rebuild only 2 spells (remember that the invisible library spell is already determined). But then, if TP is in the library slot, we will never get it with this reconstruction. We will only get it by building the library.

Option 2. Rebuild all 3 spells together with the invisible library spell. Then there is a chance to get any valid spell, including TP, if it was in the invisible slot.
But here, the probability of digging is different than in other cities. I'm not good with combinatorics and probabilities, but at first glance, it seems that in this case, digging in the Tower becomes less effective than in other cities (I may be wrong).
Even though we dig with 3 shovels, we only have access to the results of two.
The results of the 3rd shovel are discarded until all spells are exhausted and everything starts over.

Which option to choose?? I prefer option 1.

In 1.38+, only visible spells are dug, and the invisible library spell is not taken into account at all, and if we build a library after digging, we may see two identical spells at the level.

Added 22 minutes ago
It turns out that rebuilding a Tower with an unbuilt library will have a disadvantage compared to rebuilding other cities.
Question: is the option to disable the library slot reconstruction still needed or not? Because with the disabled library slot reconstruction, rebuilding in the Tower will be worse than in other cities with GM4/GM5