Should be nice to be able to automatically merge 2 or more password databases.

Use case: You have a KeePassX database on your PC and a database on your Phone, you "sync" them with Syncthing, Dropbox, whatever and you will lose changes on PC or Phone version so you need to keep both databases aside. With the Merge feature, you open both database on KeePassX and merge them so now you have all password in 1 file.