A courier system. Maybe not as needed currently but some characters like Hretha, for example, become upset when your character misses their pregnancy, it could also be used for letters from npcs you've befriended, for flavor or if you haven't seen them for some time. The courier could either be faceless or have a generic sprite, so it doesn't annoy people you could have a toggle, but could also be useful for quests in the future if you ever follow a non linear progression. Could prevent having to backtrack through every possible location to see if anything needs to be done, could add a little extra life and connection between all areas to make it more immersive. Would be temporarily disabled during sieges or major events so you're not fighting a god or something then have someone sprint in and announce "Let's see here... For your eyes only." Could possibly make a unique npc questline to help say, a centaur start one up first, but that might be annoying or cause problems. Having messages from characters in like zone A while you're in zone B or C could just help really make it feel like you're in a world, hide the curtains some if you will. Some characters like Kiyoko are more independent for the most part and make sense, but especially in more major events that have popped up of like spoiler attacks on your home end spoiler etc, could be a bit more interesting. Something that wouldn't force you to drop everything if you had something important to do, but a system where you could get more emotionally invested, like "YOU NO TOUCH FAMILY", give the illusion of time sensitive stuff so players get more invested, and if characters get upset with you for missing actual time sensitive stuff it feels earned and like you messed up instead of just being like "I mean you couldn't have sent a letter or a runner or a bird or anything?"