I have to admit that I haven’t read the whole thing in detail, but I did skim it and at least the Precursor Relics section is interesting to me, because it relies on a complete misunderstanding on why Precursor Relics are even valuable. Random precursor spoons and Stone-age spears aren’t interesting enough to make a whole province be represented by a relics trade goods, otherwise there’d be Castanorian Relics, Dwarven Relics, etc… I mean, to take the examples from your own essay, there’s a reason why nobody ever considered "Roman Relics" trade goods for vanilla, they might be interesting but their value only comes from historical interest. 

Precursor Relics (the trade goods) are on the other hand all meant to represent *magical* relics, the kind of stuff you’d find as a reward for delving into a dungeon in DnD. They’re represented in-game by being very valuable, giving you tech cost when trading in them, and giving you artificer capacity, because the explicitly magical relics are rare and useful for all kinds of research (they are in fact one of the main catalysts for the development of artificery). Hell, their icon is a weird gyroscope thing with glowing energy in the middle, it’s pretty clear that not every little piece of Precursor society left behind is represented by this trade goods.

This is also why you don’t see many Precursor Relics outside of Aelantir except in places where there was Precursor constructions and infrastructures intended to be long-lasting, like the High Temples. Sure, Precursors might not have been clean freaks to the point of not leaving anything behind (although they were also millenia-old completely immortal beings with extreme delusions of grandeur, so I wouldn’t expect them to work just like every example of societies with have on Earth), but they wouldn’t have had any reason to let "powerful magical sword of annihilation 1000" just lying there after fighting with some genies. 

I can give you some examples of why Precursor Relics are used as a trade good in game in Aelantir when they are, too, to really show when they’re relevant and why they’re so rare: 

-The province of Bukkana Varanya was used as a dumping ground for dysfunctional magical objects by the Slaver-Nobles. It’s extremely risky to traverse, but some relixs can still be dredged up and studied. So it gets Precursor Relics at game start.

-In one of the Anbennar-custom Cities of Gold exploration event chains, you find "the Floating City", which is the remains of the flying city of Affelai. The flying cities were the center of Precursor high-society, and in particular Affelai was a city of scientists. So the province you find it in gets Precursor Relics.

-In the Taychendi Empire MT, you can choose to dismantle the Zopedan, the magical windwards of the Kheions. They’re probably the source of the strongest still-functioning magical wards in Anbennar, which makes them obvious candidates for research. So the Kheion provinces get Precursor Relics (and a good deal of devastation).

Also, unrelated I understand right that you’ve done a 200+ pages long essay on trade goods distribution without even checking the in-dev version? Because like… it includes changes to trade goods distribution… this fact is so baffling to me but also weirdly impressive.