I thought this would come in the last update because I heard rumors but as we can see it hasn't. Someone who is very good at farming dark elixir can have their King and Queen upgrading gradually throughout the week. But doing this will have you at a disadvantage in war. Every other structure works while it's being upgraded why should we opt out for progressing. Example: army camp upgrading to level 5 but you're still able to use the maximum capacity of level 4.
How it'll work:
•While your Hero is being upgraded you will see his health bar, level, and time remaining for him to be ready. Before attacking it'll let you know whatever troops you are missing but the Hero if recovered shouldn't be flagged red.
I don't see why this hasn't been added already but I don't see there being an "upset in the balance" of CoC. Please any questions, comments or support so SuperCell can see



