Pairing isn't really a problem.
All of the secure sensors we sold were paired with the host. Some of them used public key processes to assure that the sensor would only work with a host from the particular OEM - not our choice, but they were writing the checks.
Apple chose the path of pairing at manufacturing - so replacing the fingerprint sensor is not something you could do as a third-party repair. That was their choice.
Pairing a new sensor can easily be done securely on the screen, but OEMs chose not to do that. In our architecture, swapping out a sensor generally meant that the data encrypted by that sensor (for example, the fingerprint templates, as well as credentials that signed you into the host) were lost. It was not possible to replace the fingerprint sensor and immediately have access to the host. You could, however, replace the sensor, log into the host using alternate credentials (password, etc) and enroll. If you didn't have alternate credentials, well, you had a problem.
I doubt very much that any current generation mass market fingerprint sensors (other than Apples, if they're currently shipping fingerprint sensors in anything) implement this level of security.