How to solve the problem of not being able to use upgrading heros in war
Before I post my idea you have to understand supercell will not just one day allow you to use ur heros in war. They make huge profit off people gemming there last days of the upgrade so they can use them for war.
I propose that supercell charge 20 gems per hero to allow you to use them in war if they are currently upgrading. It's a fair price to pay and I personally think supercell will profit more off this option as people are still going to gem there heros for everyday use