Make trade gold and inventory gold the same
I can't imagine that this would break any mods or the game. The only difference would be that traders have [more] money in the inventory.
Another maybe less invasive option would be having functions like oID->GetTradeGold and oID->SetTradeGold.
The background: I'm making a trader and want to ensure that it has the same amount of money every time the player is able to visit it (there are conditions). This is simply not possible right now - the gold respawn for traders is no option here.