Here's one simple class mod for your enjoyment.
https://www.mediafire.com/file/dzrb18c2hs5req3/SD_Classes.zip/file

Mostly, this adds several classes that are locked to a few races each, so there's more unique options for character development, and more differentiation between races.

To install, unzip into the   users\<UserName>\AppData\Roaming\Strive for Power 2\mods folder.

Are the classes balanced?
Not at all

Are some of the classes redundant?
Absolutely!

Here are some additional comments regarding mod making.

The classes editor is missing the "conflicting class" option.
resist_<element> bonuses aren't available in the class editor. Luckily, one can edit the text directly.
The json files created by the editor have no line break, making them a pain to read.
The word "avaliable" is used in the game and in the editor. The correct spelling is "available".
The class icon selector cannot search one's HD, only the Strive for Power 2 folder. Additionally, it doesn't handle .import files, so one can't use icons from the game itself.
A lot of lists are long and could benefit from being sorted alphabetically.
Mods should be able to change game variables.

This is very cool and I love that you shared it. Thanks!!

I think there's a huge amount of potential here - even giving different races different names for overlapping classes is a neat way to increase replayability and to minimize min-maxing (or maybe maximize min-maxing haha).

Thanks much.

I'm glad someone likes it.

There's more that can be done with mods, including changing races themselves, changing town shops, adding new dungeons, quests or skills.
You can also give an alternate name to a class for a specific race, although I don't think you can have a different name for each race.
There doesn't seem to be any way to add new enemies or items right now though.

I would be willing to try modding other aspects of the game, if there's anything that interests you.