It's always been like this though, and players have managed to get along fine.
The way I see it, not having one of your heroes is more or less a minor inconvenience when raiding for loot/trophies. Sure, it's nice to have them, but it's not that different than if you don't feel like waiting for them to regenerate or spending gems to do back to back raids.
Does it put you at a disadvantage on defense? Yes, but not any more than taking down a defense piece. And sure, it puts you at a disadvantage on offense too, but that just means you have to attack slightly easier bases or settle for 1 star instead of 2, or 2 instead of 3.
It really only became a problem when Supercell introduced Clan Wars, because players didn't want to put their entire clan at a disadvantage. It meant players were leaving their clans, or now outing out now that there's that option. Supercell has also said they're working on letting players have their heroes available for offensive war attacks, but its not an easy change. Aside from that, I don't really see them making any changes to the upgrades as they stand now.





