I maintain you are on the right track and are asking the right questions.
In short, the best option for the roasters will be to take up the certified stocks as the best choice for Brazil replacement. BUT these are all hedged in the futures. Centrals are sky high differentially and wont help much unless futures get to 150-180 which is likely. Roasters have maxed out their usage of robustas in their blend already.
Note too the macro: swap dealers and Index traders (investor class) dominated the COT last week; this is likely to continue. Given the favorable technicals we should anticipate 30,000 new buys from the swap dealers alone. I fear the index and swap buyers will take the mkt away from the complacent roaster. To top it off the balance of Jan will be dry in arabica areas and Espiritu Santo. A perfect storm continues to gather.