Something that would be a nice addition to this mod is some form of scaling as time passes.
Currently, this can be done by changing out the config file and then restarting the server, but that's a bit jank in my opinion.

I came up with one way it could be done from the configuration side. This assumes that logic like this can be implemented within the mod as well.

First is a switch for the whole mechanic.

Then, the more important part.
For ConfigVariant 1, I can imagine the following:

Instead of picking a random wave size from 1 to the max, it sends an amount from the given range based on where the world day count is, compared to the start and the end. At the end day, horde size is max.
The amount of waves could scale similarly.

For ConfigVariant 2, an additional list could be given.

HordeDifficulties would dictate the pace of the scaling, which hordes are permitted to spawn and the amount of waves, possibly influenced by the additional wave chance.

Now that I wrote all this down, it's starting to feel like that these might be better as new config variants instead of altering the already existing ones.
This is only an idea of how it could be made, but I have 0 experience when it comes to designing these things.. I just hope that I can give inspiration with it.

Thanks for the input, difficulty scaling is on my todo list :)
I also thought that probably an additional config would maybe make sense.