Is it possible to increase the number of creature slots from 7 to 10 in castles/for heroes?

A very interesting idea with alternative creatures, but it would be easier to implement direct creature progression.
For example, there's a Peasant dwelling, and it has 5 versions.
Grades 2 and 3 can be moved to level 9 or 12 of the town and made dependent on the Peasant huts of the first grade.
Then, at higher levels, you can completely remove the weak peasants from the army and replace them with, for example, halberdiers.

This could be a good idea. However, there's one catch: it's likely that it won't be possible to upgrade old creatures to new grades through the town. The game might simply not recognize the connection between them.
Added 2 minutes ago

So, as a newbie in working with .Exe files, it seems to me that this is possible, but whether it's actually feasible, I think those who created the frameworks will answer. Perhaps in the future, when they take a look at this topic.

I'm also a newbie, for the most part. But it seems to me that this cannot be done without the source code.

Added 37 minutes ago
Wow. I tried it, and it turns out it's possible.

https://yadi.sk/d/-X_eLdQ3nkkWSA

I wrote it as a test: the third upgrade for the Peasant building. For the test, they upgrade to improved Gremlins.
At first, the game didn't want to link these creatures, but then I wrote Gremlins as upgrades in the improved Peasant files. And it worked.
In theory, you can build two more upgrade levels this way. It's pretty cool. You can make a whole bunch of creatures available to the player.
And most importantly, it's very easy to do. If anyone is interested, take the test archive that I posted above, and see which files and how need to be changed.