Spoiler: What is all this? All I want to say is... Personal project, and... are you guys hearing that Σcho?
Sadly, [n = 3] is the max tier I can tesselate, in Minecraft, without FPS going to the negatives. However, a pseudo-menger (2-dimensional with opaque center textures, on each side) will likely be used, to solve the rendering issues, as that means that the faces on the inside would not be rendered. To make it a bit easier to understand: a wavefront-object model (.obj) for [n = 3], is 1.3MiB large, with the most optimizations possible) The cube amount in Menger fractals increase by 20 times per iteration. The smallest a [n =6] (top tier) model would thus be is 1.3 * 20^3 MiB large... And we all know the probability of it actually being the smallest possible size is... (I am using IBakedModels however, which are part of Minecraft's own rendering system. I create these when required, and cache them, for later use, instead of scrapping and re-making them; much like Agricraft does with it's wooden blocks) [n < 6] renders fine now, though without the 3D effect. Last tier still makes Atlas' holding-up-the-sky seem like nothing.... Might create a custom non-menger fractal model for that last tier, though I wonder who will ever get that many blocks legit (not counting cobblestone)... 20^6 = 64,000,000