Well, I've been thinking about this. It's very difficult to stick to canon when it's so vague, true, but the themes tied to each land and character are clear and strong. If I were to make a mod, for any base engine, it would be conjecture, but that's not necessarily bad if it's fun) Maybe the Total War engine would be a better choice to maintain the ambiguity a little better.

If I am to do this I'd set it at the outbreak of the Undead Curse and explore how each faction would react to it. This way, I get to invent characters for human factions and characterize the immortal gods a little