Just a thought, and of course we will have to see what they have planned for higher tiers, but this wouldn't be much different from a recipe change. Altering the lower tier requirements to need more of a single resource instead of multiple types and adding new types of goods for each tier above. This could leave the 6 available ports open for the highest tier. Each upgrade could increase the amount of previous tier goods to balance out the difficulty.
As much as I enjoy having my containers full all the time, I feel having my factory feel constantly alive would be more appealing. I've simply found the further I progress, my older machines start to idle before my highest tier automation is complete. Much like Factorio, even red science packs are required for end game upgrades.
This change wouldn't necessarily be to make the game easier or harder, but rather to keep my old machines working with a purpose. It could add an even greater need for base planning for expert players, while still giving beginners a feeling that what they've built still matters.