Spawn less gold blocks in Bastion Remnants

Hello, I'm currently developing a UHC datapack and I want the option to nerf Bastions so they have less gold blocks than usual. I found a temporary solution by replacing nearby gold blocks around the players with gilded blackstone, though this is not exactly what I'm aiming for, and I don't know how to do any better using commands.
Is there a way to achieve this using commands or should I directly modify the structure? If the answer is the latter, what would be a somewhat easy way to begin modifying structures? I assume it's the more practical solution but I've never done it before.