It's really not that hard to keep a mental lookup table for each person and their custom pronouns and declensions.

Another pretty elegant solution I've found if there's too much confusion amongst our team is to suggest people switch to learning Hungarian which doesn't have gendered pronouns. A few years of intense study is a small price to pay so that we can avoid the catastrophic mistakes of accidentally calling someone who's not in the room the wrong gender

Unfortunately I tried that. After 3 years of Hungarian classes, I had a peer that demanded I speak to them in Klingon because they identified as hypermasculine. Now I have to start over again.