Companion App - Raid Warnings, Servant Controls... etc
Similar to how Rust has a companion App.
This is a big request, obviously developing an App and deploying it for mobile use on Apple or Google play store.... BUT it would provide another layer of depth to the game and keep people engaged even when away!
The App could provide warnings if your castle is decaying, or being damaged during raid times.
The App could show your clan members (who is online etc)
The App could allow you to check on Servant Missions (maybe even send them out again?)
There are many uses for an App like this, and it would likely only be able to work with supported servers.