Harmony - Troop Symmetry

I didn't mean that Town Enhancement (TE) should replace unit upgrades.

I don't consider myself a strong Heroes 5 player; I only play as Humans, Elves, Mages, and Necromancers... and I don't know how things stand with the other three races regarding unit upgrades, but I want to say that I don't see the point in upgrading units for Light Elves, Humans, or Necromancers because of their upgrade tree. Because a set of various disables, especially in combination with the right artifacts, is more useful and applicable in a wider range of situations... both against all enemy races and in clearing the map (especially if the map is complex, not just empty).

My recommendation:
TE should tie the race to the magic of its castle (one school) and to "non-combat" skills that are equally useful for all races - i.e., logistics, education. These three skills should be for everyone. Moreover, learning TE should not prevent the player from choosing which magic skills of their race they want to learn... if this is impossible, then, in my opinion, it is better to go through three main magic skills of the race (as it is now with TE for Light Elves in fire magic).