Hello,
I'd like to suggest that goods should have shelf life or expiration.
This suggestion comes from my observation that producers can dominate the game through cartel.
While in reality, some industries may show cartel, still they are bounded by the limitation of the shelf life of the inventory (albeit long for some and short for others).
Simplifying things, I'd suggest that there is 2 phases on the inventory's life.
First is the fresh phase.
The inventory will have a time which ticks like a bomb until it reaches the rot phase.
Combining 2 sets of inventories with different freshness time will result in 1 inventory that will have the weighted average of the 2 sets. Weighted by the units.
When the Fresh Phase timer is zero, it proceeds to the rot phase.
Second - Rot Phase
The inventory will exhibit a half life. Quantities will decrease by some factor every certain time.
Inventories in rot phase will never be combined with the fresh ones. Because in reality, we always wanted this two separate.
Another industry may arise from this, like recycling or some sort.. or not.
But I really think there's just a lot of unused inventory in game. Also retailers can just deal with the cartel and producers can stock up on inventory indefinitely without consequence.
Hope you read this and consider.