Construction material downtrading

I'm thinking it may be worthwhile to implement instant unity trades of 20:10 T4 to T3, T3 to T2 and T2 to T1 construction materials somewhere.
If something has gone direly wrong, you have a stockpile of more advanced materials but physically can't make lower-grade construction materials, this would help you get a handful of lower-grade materials to build what's missing (e.g. downtrading T3 to T2 to get a cargo dock built).
The unity cost and loss of the added materials should help avoid having players freely spam it and still carefully think through their balance of production.

I can see this, especially with your idea of a higher cost to avoid spamming it.
When you absolutely, positively, need 100 of a T1 resource, you'll gladly trade 100 Glass for it!

Quite often when u rebuild u get a bunch of extra high-tier construction materials leftover (while mats go in and out, production buildings fill in gaps resulting in extra mats that do not fit into the dedicated storages by the end of the construction project). So downtrading may help, but not much - I'd rather like to have options for trading out the high tier construction mats for some generic goods.