Just make shit up. Just do der/dem which will confuse the fuck out of people.

There‘s a reasonable proposal for „en“, so you can just use that

The german language is not bound by the laws of some institute, you can just use whatever you like!*

* Not applicable in schools in saxony, bavaria, schleswig-holstein, and saxony-anhalt.

Maybe ze? The way "they" sounds with a German accent?

I like how Japanese does it (at least based on a likely oversimplistic explanation by someone who makes 4+ hour video reviews of games like Pac-Man [yes, Tim Rogers]).

From what I understand, every time a person refers to themselves or someone else, they choose which pronoun to use to fit the situation. That is to say, their social stature compared to the other person's, their age compared to the other person's, the general circumstances, etc. Similar to how their honorifics work (suffixes like -kun, -san, -sama, etc.).

So for example, while there is a specific pronoun that is typically used to refer to a young female, if there is a young girl in a situation where she's trying to make herself feel stronger and older (I'm picturing an internal monologue here to hype herself up I guess. I'm too brain broken to not imagine all of this going down in a JRPG), she might refer to herself using the pronoun typically used by grown men.

Again, I don't know Japanese, so I can't give specific examples, and I could even be completely wrong, but maybe someone who knows the language can elaborate on (i.e. correct) what I said. I found it to be a very interesting way to go about it.