I'm not a mod developer, yet I keep thinking of great mod ideas and decided to share ideas, hoping a mod developer picks up on them.
I thought since we already got a DLC revolving around death and disease, why not add a camp purpose dedicated to curing pandemics across the map? It shouldn't be too easy but perhaps offer prestige, popular opinion & gold.
Trying to cure the bubonic plague would be in vain. However perhaps the entire camp can still gain learning from their failures.
Perhaps the whole world could also experience a massive development boost two decades after the plague, as historically the massively population drop allowed for more resources and individual growth (contributing to the renaissance).
Technology progress overall could be slowed down to balance this (it progresses too fast anyway).