IMHO, I disagree with your argument "for loyalty programs to work, merchants have to know who's buying from them".

Only partially, they have to be able to IDENTIFY them, which they can still do with a token, as long as the token has a persistent relationship with the unique customer. (Note, it does not in several tokenisation models, which cite added security by giving the token a life or use cycle - in my opinion an uncessary restriction). The detokenisation can be done in the distribution model ( either print or interface with merchant/consumer). This placing of detokenisation at the very perimeter of the system is one of the out of the box features of Chasm Management Limited's PCI Envelope business model.