The infamous "using heroes while upgrading in war" problem. A different solution.
So I get why SC wouldn't want make heroes usable in war while they're upgrading. They are a big part of a successful attack and the more incentive to gem the time the better for SCs wallet. I've gemmed hero upgrade times a couple times myself, so I'm sure they get a lot of income from that.
Thus, I am not asking for heroes to be used in war. It probably will never happen, and if SC is considering it, my one thread out of the thousands that exist won't influence anything
No, I have a different idea on how this can be somewhat "resolved."
The update a couple months ago made it so that walls and heroes get "weight" in the clan wars matching algorithm. For the most part, I think this was a great addition, because walls and heroes can add a lot of defensive and offensive power to a base, so it makes sense they have weight.
Now I'm not sure how much weight heroes add, but I'm guessing because of their power, especially in higher levels, the weight added is pretty significant. This causes a problem when you are upgrading a hero, and you can't use it, but the weight is still added and makes you matchup harder, while you are at an offensive disadvantage. That would be like an inferno tower being upgraded, but it doesn't work in war during that time and the high weight is still added. Gives you a big disadvantage.
My idea is to remove the weight of the upgrading hero during the time it is upgrading. This makes it so that you won't have added weight for something that you can't use. Or perhaps cut the weight in half during the upgrade time because the hero can still defend, so removing the weight entirely can cause problems too.
Now I know that it poses the possibility that you start a hero upgrade, start war search so hero weight isn't added, then gem the completion time after you've found a clan so that you have an available hero without the weight. However I don't think that will be too common. After a while, you run out of hero upgrades, so people can't do this indefinitely. Also, the cost of finishing a hero right after starting the upgrade can be significant gem-wise, which means it can also be significant real money-wise.
Also, I have no coding experience or knowledge, so I have no earthly clue how hard or easy this would be to actually implement in the game, so I apologize if this idea is just too impossible to actually do.
I know its a long read, but I hope this idea can get at least some consideration. At the very least I hope it is a nice change from the thousands of rehashed make my hero available in war threads.