I did this in a novel I wrote, actually. I assigned TLA 'names' based on their job (ENG, PIL, etc), and any time a gender would normally be referenced in the text I used XXX - both for easy searching. I got about 70% of the way through when my beta readers rebelled - they absolutely HAD TO KNOW what gender everybody was. Sigh.
But by this time the characters' personalities and speech patterns were well established, so I flipped a coin for each one, and continued onward. I'll probably do this again some day and just ignore the beta readers.
Pencil and paper.
As a gryphon who is very tired of seeing dragons everywhere... I love this.
I really enjoyed the few games of (1st edition) Traveller I got to play. Most fun I've ever had dying during character creation. Repeatedly.
Why would they need to make sense? That's clearly not a requirement here.