Reading through Allik's explanation of Connection as a Feruchemical power in Bands of Mourning made me consider that Feruchemy is not a system of Preservation or Ruin, but a hint towards the more pure workings of magic in the Cosmere.
From the Coppermind "Duralumin stores spiritual connection. Reducing other people's awareness and friendship with them during active storage. Tapping it can help speedily forming trust relationships with others."
In Bands of Mourning Allik uses this ability to speak with Wax & co, even though he is from another part of the planet and doesn't speak their language. Marisi then subsequently tries to use the same trick to speak to Allik in his own native language, but this does not work. It is then explained that connection is intricately linked with geographical location. Marisi cannot speak Allik's language because she is being connected to the land that they are in, her own home.
This made me think of the location based powers in Elantris.
Also, coincidently, there are 16 shards and 16 Feruchemical properties.
So my thoughts are, can we create links between these two sets of 16?
It seems clear that if Duralumin/Connection = Dominion, then Necrosis/Investiture = Endowment, as the magic system on Nalthis is entirely based on shifting around investiture.
I haven't been able to think much past here.
Preservation could brass for the warmth felt when burning metal, or perhaps copper for storing (preserving...) memories?
Cultivation could be gold for health.
Devotion could be electrum for determination as the power is granted to people who are particularly devoted to something.
Or perhaps Ruin is copper, as when memories are accessed they degrade, which seems to be the only Feruchemical power which does this?
Anyway, interested to hear anyone's thoughts.