With the new world layer of grimstone, many have noticed that strongholds exclusively generate at that level and thats great! Strongholds should intentionally generate deeper in the caves to make it harder to get to. Meanwhile, it should be fair that mineshafts should generate exclusively above the grimstone layer to give player progression. As you go from the comforts of the mineshafts to the terrrors of the strongholds. Also giving variation to these two structures would be amazing. Having mineshafts generate with different woods would be interesting as well as making strongholds out of grimstone bricks and toles would fit the mixture of end dimension and dark underground vibe!