The fourth column in mercenary towns.

Question: why create a fourth upgrade path (an additional alt) when most of the existing ones are poorly implemented? Are you familiar with Occam's razor? There's no need to create unnecessary entities. If you want more variety in the alts, diversify the creatures by assigning them to different paths, making more distinctions between them, and giving them different stats and abilities, etc. For example, there are Titans and Thunderbirds. Why do we need another alt when, in reality, there isn't even one good one? Another example: Succubi and Temptresses, Royal and Battle Griffins, Assassins and Hunters – this is how you should diversify the alts, and that will provide the desired variety without adding 100-500 unnecessary upgrades that few people will use.

Added 4 minutes ago
Of course, everything mentioned above is just my IMHO.

As I understand it, we're talking about additional alts, not a sequential 3rd upgrade. 5 levels of buildings sound good, but they still need to be rendered (i.e., unlocking the potential of cities requires a separate project).

I think it can be done. First, Dyrman recently discovered that ALL city buildings theoretically have a fifth level (like the guild). And that means, as I understand it, it's possible to create the next level of upgrade. But I wouldn't give it to all creatures, only to a limited number, as it was in the second game. Otherwise, there will be too many.