Rooms spawn much rarer than they should + no guaranteed library

[AverageUser67]

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).

[jackschedel]

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.