I have a few questions.
Neutral monsters constantly spawn; is it possible to set a fixed number of monsters? Otherwise, I have to place key monsters using the red player. It is possible to make neutral monsters change ownership by assigning a trigger script to them and setting an event containing this script. Can it be done so that neutral monsters join upon discovery, but a battle doesn't start afterward? It seems silly to fight against yourself. And finally, can you force a player or hero to switch from one flag (e.g., red) to another flag (e.g., blue) in other editors? It is possible to switch a neutral monster to a flag, but how about a hero owned by a player? This couldn't be done in the first version of the editor.
With a monster: it's better to place a trigger within X tiles of the monster so that it doesn't attack, and create a trigger when the neutral monster's ownership changes. Otherwise, I don't think it's possible.
Regarding the hero: if there is a trigger, then it is possible.