Maybe join the 2.0.4 beta to see if that helps?

Run the mod (without any other mod) in Beta 2.0.4 version.

引用自 Jiggy：

Run the mod (without any other mod) in Beta 2.0.4 version.

Not to sound dumb, but how does one change their launcher to Beta 2.0.4?

Nothing to sound dumb in that.
Right click on your game in library, click properties and then go to Beta. Select 2.0.4.
Sharing a general video about it:
https://m.youtube.com/watch?v=rNbBx1UY5go

Thanks for the tip, tried it out, but sadly it did not fix the problem.
I have: updated drivers, checked the integrity of the steam files, and redownloaded the game & mod, but to no avail. The game (with mod) runs, but when I press "New Game" it loads to about 18-19% (according to the loading screen counter above) before it crashes.

Okay, here is what I suggest, assuming you deactivated/removed all the other mods.
1. Remove this mod (again ensure none of the other mods are active/subscribed)
2. Go to properties and verify the game files (ensure you are using 2.0.4). Wait for few mins as it really takes times
3. Restart your system
4. Re-subscribe to this mod
5. Again verify the game files
Then let me know if it still does not work.

Usually game crashing mid-way when using a mod is probably because of come conflict.

I know this is repetitive, but I am able to play it in a potato system.
And I need to close all other programs, including this steam window when I play Imperator: Rome because of it's resource demand.

引用自 Jiggy：

Okay, here is what I suggest, assuming you deactivated/removed all the other mods.
1. Remove this mod (again ensure none of the other mods are active/subscribed)
2. Go to properties and verify the game files (ensure you are using 2.0.4). Wait for few mins as it really takes times
3. Restart your system
4. Re-subscribe to this mod
5. Again verify the game files
Then let me know if it still does not work.

Okay, I tried it, but it did not work. I have also deleted all my mods alongside the game, before I redownloaded the game and this mod (and restarted my pc).
The game keeps crashing sadly. I can play other mods (Terra Indomitus, Invictus etc) without problem. And my pc is definetly no potato pc. I am thinking of deleting steam and redownloading steam, but I doubt that is the issue.

For anyone with the same question (why does my game crash when starting a overhaul mod) > delete your paradox files in your documents folder (if you're on Windows). This sadly removes all your settings + save games (you can back them up online)