The pillars are a thing, and having marks to match would be very cool.
Quartet marks would be very useful to extending deck building to include multielment decks with one element outside of the quartet.
E.g. you could run a material mark and gravity pendulums to make a lava-togs.
This allows building decks that rely on an off quarte element as a "Main" element while being able to easily power abilities from within the mark quartet.
The georesonator interaction could be very interesting as well.