HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

Actually, all of the above made me think about implementing an option to leave the weakest creature behind (i.e., simplify the algorithm and make it less intelligent).

I think that's a good idea. It would be easier to know what will be left and be prepared to make changes. Although, I'm quite happy with what we have today. Replacing one unit with another is not difficult.