With regard to the kami angle, I'd point to two pretty strong citations that it was intended.

The first is that the 1.0 Japanese language uses 1:1 Shinto terms to refer to elemental-associated stuff. Concepts like [purity as consistency with natural order], [purification of impurity as a communal responsibility], [pacification of spirits], [impurity as the source of spiritual wrath], etc. were all present. Gridania was Shinto through a lens but then Hingashi came along and did it without the lens in a different way.

The second is that the developer panel just before 1.x launch described Gridania as "inspired by an ancient Japanese polis".

Incidentally this is a big reason Gridanian culture gets misunderstood. If you can take it for granted that the elementals are real, that impurity is impurity regardless of "fault" and that it is the community's responsibility to purify it, that the presence of impurity causes the elementals to enter a wrathful state regardless of what they would otherwise "want", and that elemental wrath causes the forest to become agitated and violent and brings disaster, then it makes a lot of sense why Gridania is wary of outsiders, doesn't trust them to protect the community, is afraid of the calamity they might recklessly bring on the community, etc.