Since the question seems to be subdivided, I will answer it with a quote.
The behavior of the reinforcements in Chapter 7 have been inherited from the original Eisenau’s. However, there is no storyline necessity, so it might be better to allow the reinforcements to continue to appear.
As the story explains, Ishtore is not allowed to cross borders. Therefore, he does not move.
I have not seen first hand the twists and turns of those developments, but from references to one topic, it seems that some people are taking DMCA action against projects using PE text, and I don’t want to get involved those.
I did not test this pattern, but I am glad the vanilla program handled this without problems.
Poison weapons cannot be used by the player to inflict poison. (As in the case of the Yotsumungand.) Thus, even if you can get a poison weapon, you will just have a weapon there that is less powerful than the iron weapon. I can change the process so that the poison can be inflicted for enemies, but should not do so because there are several situations that would be easily handled by a frame-up, such as inflicting poison on an enemy that is not moving and leaving them.
I know that such class names have been adopted in localizations of the later series, but the FE4/5 class names are unique in Japanese, unlike the other titles. Here I gave preference to how they are called in the original Japanese.
In Japanese, Myrmidon (after FE7) is “剣士” (Swordsman), but “ソードファイター” (Sword Fighter) in FE4/5. Brigand is “山賊” (Bandit), but “マウンテンシーフ” (Mountain Thief) in FE4/5. And similarly, I did not make “マーシナリー” (Mercenary) into “Hero”.
Currently there is no one who can be Barbarian. There are several other classes dedicated to the enemy.
I intentionally reduced the number of classes that could use light magic. Because they become more powerful as towards late game. Players can consider at the time of promotion whether want their magic user to be an active player in the midgame or to prepare them for the late game.
Units with elite skills can now equip weapons one rank higher.