Following on from my post about my hopes for new D2E things- and the fact the Realms of Terrinoth Sourcebook seems to be the beginnings of this- as an idea for your development team could you please do a series of 'background information' books that unite all the Terrinoth/Runebound games including the out of print ones ideally.
Doing so would be massively useful for the RPG setting and storyline creation aspect of Genesys but also really helpful for making D2E quests/ playing D2E if you enjoy the lore of it.
Sounds like Realms of Terrinoth does this quite a bit already so it would be great to continue down this route - an encyclopedic archive of the characters, monsters, places, items and so on from all the Runebound/Terrinoth games. Including the out of print ones as some of us have things like D1e and even those who don't would be able to use the information for their RPG ideas. (Proxying in minis if playing with minis and they needed to, it also means FFG keeping the option open of bringing that item such as a character piece or setting etc back in a future release.)
So we've got characters background and races, what the monsters are (or what people speculate they may be!, some like Skarn are unknown entities, and good/evil can be subjective!) and where they are from, the places and some of the backstory.
Linking this into playing pieces and tokens/cards etc players may have in their creative toolkit would be really useful for those working on their own D2E quests or Genesys story arcs, so maybe cover some of the relics, items and so on as well.
Tying up all the different games in this way would be truly awesome especially with how well you've built up the lore and background of Terrinoth and the Runebound Universe.
And of course it's a creative springboard for those who might take something in a different direction in the stories of their games- they know what we think we know so far but maybe there's a twist- Skarn's not what people thought it was, that bad character's perhaps not as evil as we were made to believe, maybe that friendly character is something else.... So it doesn't stop players telling their own stories, it just gives that overview and starting ideas they can then play with.
It would also really help with the fact I'm now trying to work out what races/factions/loyalties all the D2E characters are and how pieces in the different games relate so I can bring them together for the stories of my games! And what creature species the monsters are.... (you could cover monsters, dragons and so on as their generic type and notable famous specific, named ones of legend such as Valyndra, Belthir and Bol'Goreth)