This won't work because instead of extra slots, casters from the native castle or tier 1 units will simply be shared. They already share, but in the final version, a full army is assembled.
However, the opposite practice, where the number of slots is less than the number of creatures that can be built in the castle, would be interesting, as it would motivate players not to build all of them.
Regarding rare and overpowered creatures, "bosses" – this is a niche for tier 7; some players simply play on the map for too long, and tier 7 ceases to be something special, the pinnacle of development, which it should be.
Well, in general, we're getting a bit off-topic here, because the topic is about a collection of existing mods, not about fantasies about creating new mods.
I was actually talking about reducing the number of slots. This is what leads to the fact that not building everything creates a semblance of alternative builds.
And the idea about creatures isn't about bosses. Bosses are there to accommodate the rest. With alternative builds, for example, you don't want to have 7 tiers, otherwise the priorities will simply shift towards higher tiers. But what's important to me is that in Heroes 7 and online Heroes, there is a class system for creatures, and it's understandable, i.e., not like the levels in Heroes 5. It's clear that tier 1 and tier 7 are very different. But from tier 2 to tier 4, it's not so obvious. To understand who's who, you need to know the game and the creatures. What I'm suggesting is to spread out the tiers so that there's a small gap between them. A whole army should be able to defeat one tier 7 creature. But yes, this is not for short games, and that's understandable.
As for the off-topic discussion, you can ask the mod creator and his team. On the one hand, it's really a collection of mods, but on the other hand, the last poll seemed to imply that you could also order exclusives for the collection (for example, about new cities).
In general, the topic of slots has touched me. I would try it. For example, I would try to create a makeshift solution and block them with some kind of creature, a "castle." The only thing is, I know about mods at the level of tinkering with models and parameters. I haven't worked with connecting scripts. And I need a couple of your tips, Nargott. For example, do I need the Lua core from Quantomas to use it, which, as I understand, you use in your mod? Or is 3.1 enough? And also, about how to patch hex files. In general, I'm new to the forum; can you suggest who to ask or where to create a topic? In what I've found here, they mainly ask about 3D modeling.