Structures invincible until boss killed

I want to make my structure unbreakable until I defeat a certain boss or destroy a beacon inside. What I have is that when the block is destroyed it checks a bossKilled variable and if it's 0 it replaces the block with itself. When the boss dies/block broken, it sets that variable to 1. Is there an easier or more lightweight way to do this? Maybe a way that applies to each structure itself, not just specific new blocks, so then I could use vanilla blocks in the structure.