I'm building a humongous base in the Nether. Because of its size, it would be impractical to go for resources to normal world over and over, and I don't want to build portals everywhere, so I'm searching for alternatives. The resource I'm looking for must be immune to ghast fireball explosions (blast resistance of minimum 16.5 as the wiki says) and possible to obtain renewably in large quantities in the Nether.
For example, a block of emerald would do, because even though you need a villager from the normal world, you can trade with him for emeralds in the Nether once you teleport him there.
The block must be renewable in the Nether, so for example cobblestone is ruled out because it requires water and lava to be made, and water cannot be placed in the Nether.
The easier the block is obtainable in large quantities only from renewable methods, the better.
The version I'm asking this question for is 1.14.4, so ignore the planned nether update when it comes to answers.
Which of the blocks of Minecraft would best fulfill those criteria?