Just a fun idea I thought a while ago when the Workshop wasn't added.

Imagine you have, through some combination of verbs + cards a way to manually start a rivalry.
Yes, you can more or less already cause it if you so wish, but imagine you have a dedicated way to search for one, and engage them.

The idea would be to bring some mechanics similar to the Rivals in NG+ to regular games, but instead of a permanent thing, they'd be short encounters that give you random rewards.
These would then be a parallel system to Expeditions to find items/lore and maybe even followers! That way, you always had an alternative to expeditions, and you could even run both things in parallel if you're crazy enough to do it.

If no-one wants to pick that up, I'd love to give it a try, is there any documentation/help for people starting to get into mods? I already code small projects in Unity as an Hobby.