The refinery. Do it. I have read the FCC Refinery Review by Primero, which shows FCC can inexpensively rebuild the refinery.
There are a number of variables that need to be reduced to help make a sensible commercial decision.
The main difficulty is feedstock - should FCC be buying or toll-refining ore or reprocessing the plentiful muck piles?
The $26m option gives two circuits, one for raw ore, the other for reprocessing.
Trent could sell 24t/d a dozen times into N America. I think it is a no-brainer.
Timeline: 18 months. Trent, command the team to do it in six. Cobalt is in the mineral equivalent of war. 
Ash