In general, I always loved the concept in original Xcom games, esp. in strategy games like Civ and Pirates! (OK they are historicaly based, so much info could be added).
I would love to see info and anim similar to e.g. mutation reports in our Pedia.
Some more info on races and origin, like in original Xcom 199x
Also, I find messages of events, wars and site discoveries with voice overs were good story driven, as well as in game animations, and I hope these could have a replay option in Pedia. Story is well developed, kudos for that.
I know, a lot more strategy and units important to do, but please dont forget the pedia!