You might not agree with me, but still...
I had this thought... We played Heroes 5 first without the second upgrade for creatures... and then, when they added it, it became several times more interesting! Because the choice of creatures is huge, it's great... But... it's clear that in terms of abilities, the upgraded and advanced versions can differ greatly... but visually and, let's say, in essence - they are essentially the same.
Let's take, for example, the Colossus, then the Titan, and the Thunderlord... You look at them - the color is different, the abilities are slightly different... but it's still the same donut, just without filling or with a tasty filling... (I came up with this comparison late at night, lol)
Dark Elf Witches - they are generally hard to tell apart, the color is different, but in essence - it's just a woman with a whip, and that's it...
They don't differ much in essence, but visually - the Dwarf Bears, that's where I always had a hard time choosing, the Northern Bears look nicer, but the others seem stronger... The Wizards differ, but again, the upgraded and advanced versions, the Wizard and the Archmage are essentially different only in the color of their robes.
I've always felt sorry for the Rakshasa unit... because essentially, a Rakshasa is a woman, and she looks unusual, cool... but you can't really play with them, because you build an upgrade for the building and get blue or yellow lions... already male creatures.
So, that's what I wanted to say... I would make a mod that does something like this, maybe a little like in Heroes 4 - we essentially have 3 stacks per creature level: base, upgraded, and advanced. In the vanilla game, the game recognizes creatures as base, upgraded, and advanced... but the player doesn't care about that, if, for example, we make the base level 4 of the Magic Guild, for example, a Wizard, the upgraded version a Djinn, and the advanced version a Rakshasa, then we get three completely DIFFERENT creatures at one level... and the player will have a more diverse and enjoyable experience playing with them, who to take - a Wizard or a Djinn, someone will like the visual appearance, someone will choose based on characteristics, and someone will recruit both, but for different heroes...
Then, continuing the example, for Inferno, instead of "Cerberus and Hellhound" - which are essentially a dog with three heads, only one is red, the second is smoking, we can make - a Cerberus, a conditional Ifrit, and a conditional something else... and they will differ in abilities, visually, and in essence... the only thing that will unite them is their belonging to the creature level, 1 or, conversely, 7.