Title: most of the stronghold is hallway even though there are many other structure pieces available. I also noticed that the "grand library" piece isn't guaranteed to generate, which in my opinion is a shame since the library is one of the most recognizable parts of the stronghold (and some mods have items in the library loot table).

It is likely too late to change the generation weights. I think the sparsity of rooms is fine, albeit less than ideal.

The library not being guaranteed, however, needs to be fixed.