Fox suggested adapting the internal Alien Creative Bible into an Encyclopedia in 2019, then Disney took over. I mentioned it to Titan afterwards, and they asked me to pitch - then never responded. It wouldn't have been an 'in-universe' one like this though.
Even though it was against my own interest, I thought a hardcopy encyclopedia wasn't the greatest idea because it's static, while online resources that already exist are way more dynamic. And free.
It is strange that this has been in the works for so long and still not done. It must to to include the new film/TV content. And possibly reconcile whatever the TV show is doing to continuity.