Both of these thoughts involve my mod for .15, Primium. In short, it adds a new material, Primium, which can be used for nothing without dependency mods. If you argue that the value of the top-tier primium is "too little for Power Armor Mk4" then my argument is that it's over 1 quintillion.
Link: https://mods.factorio.com/mods/cpaca0/Primium.

Shameless self-promo.
THOUGHT #1: Use primium in recipes. Just as a "Resource Counter" to "itemsink".
THOUGHT #2: Tier 5 Power armor requires Tier 4, some more crap, and Primium to, again, be a sink for items to go.