Aphelia has had nearly 10000 years by herself, for some strange reason I'm not sure Proto-sentient would continue to apply to her.
nor for that matter would "sane".
but that's just my opinion.
One way of restricting block structures/ships is to change the properties (e.g. strength) of a material based on how thick it is, like how far it goes without either a different material or a gap.
probably a massive pain to implement, but still.