The idea of rebalancing and reorganizing the neutral creatures into a new, unified list is good and correct.
However, in my opinion, many creatures from the current neutral creature sets need to be cut using Occam's razor. No offense, but I don't think there's any need for several dozen creatures that are unremarkable either gameplay-wise or visually. This is one of those cases where more doesn't necessarily mean better.
I think when dealing with such things, you should ask yourself: "What interesting and new features does this creature have?" "Does it look interesting visually? Does it have gameplay value?" "Is it really needed in the game? Is it redundant?" Too much monotonous content is also bad. Players simply get tired of 20 hastily recolored minotaurs, and few will want to delve into the nuances and remember what the difference between them is.
Anyway, good luck with your build; it will be interesting to see what you come up with.
If you need them, the models of creatures that I ported from Heroes 6 and 7 are at your service. Just please, if you use them, read how I asked to use resources from my mod and do as I ask. That is, copy the archive with the "clean" resources to your mod without changing or renaming anything, and then make changes on top of that.
If something comes up, feel free to contact me; I'll try to help.
In general, there are always not enough good, interesting, and balanced creatures. So that a creature isn't just added for the sake of adding it but is actually appropriate. So, it will be interesting to see what ideas you have. Maybe some cool gameplay idea will emerge.
Added after 10 minutes
In general, for such a thing, it would be nice to somehow update the neutral creature list. Many players don't see any value in them because they are simply neutrals. It would be great to give players the opportunity to regularly control these new creatures without replacing the original creatures from the castles.
I already described the method using alternative buildings for hiring in cities; it works quite well.
/topic/at/1009839/
However, it's unclear how the AI will behave with this method. It's possible that it will act very stupidly.
I'll try to put together a working demo in the future and test it.
By the way, if anyone knows scripts and wants to help, I will be very happy.
I will imagine that no NCF existed and start creating my own as a balanced system. Of course, there aren't that many abilities in the game, but I will try to maximize their potential. The use of neutral creatures by players is planned through dwellings that will appear along with mills and gargoyles via the Global Strategic View (GSV) and are available in the editor.
I started working today, and managed to sketch out approximate concepts for the first 160 creatures. There isn't as much free time as I would like – work, etc., so the mod won't be released in a week or two; you'll have to wait.