Using Eradicators Character Additions, this mod just defaulted to the standard Factorio player model, regardless of what armor I was wearing.

What mod categories should I try to deactivate to see what mod causes the issue?

I believe there are no separate animations for different armors. Try it without eradicator's mod and switch armors.

It works with the one other Character Selector Mod I found ( the one with the vaporwave icon ), but it kinda deletes the entire inventory in the process of switching which is "sub-optimal".

Guess I will have to stick with Eradicators and other chars :/

It works with the one other Character Selector Mod I found ( the one with the vaporwave icon ),

Would that be this mod?

I must apologize, I seem to have not seen that character selector.
I've used https://mods.factorio.com/mod/RitnCharacters , but as I said, not really suitable
If your mod works with your suggestion, I should be fine

Thank you for your help!

Sorry, clicked the wrong button when tried to edit

I must apologize, I seem to have not seen that character selector.

I've updated it for Factorio 1.1 just about a month ago, that explains why you may have missed it. :-)

If your mod works with your suggestion, I should be fine

Screenshot from the info page.

Thank you for your help!

You're welcome!