I would suggest something else seen in many other games. Leave the original dungeons as they are now. As soon as you finished all the levels, reset the dungeons and give access to beginner, intermediate and expert level.
A beginner level would be a dungeon without boosts. I would replace gems, vouchers and monster rewards by gold or something like that, since a player who was able to beat all original dungeons, will also be able to beat this one, that’s why it is a beginners dungeon.
In intermediate level, only normal boosts are active. So no war boosts (also no doom gate! that’s a war boost). For most players this is still doable, but still it could be a challenge.
Once you complete intermediate, you should go to expert mode. Normal boosts plus war boosts can be active. Gems and voucher rewards I would add here. It’s difficult to complete those dungeons and should be rewarded.
It should be easy to do so, just keep dungeon design the same. Only activate or deactivate the boosts. And for players this is hours of extra fun.