DM-27167 concluded that the only aliases being used in the current Stack are the afw_name fields (HSC/r2, HSC/i2, DECam/SOLID), which are used as the canonical name for old-style filters and therefore written in exposures and catalogs. Unfortunately, we can't remove use of these names in a self-consistent fashion without breaking some code, somewhere, that depends on the current hybrid system.
John Parejko suggested simply adding special-case code that detects these three names on reading old Exposure files (in addition to the band vs. physical check discussed on RFC-730). There is also some special-case code surrounding these names (https://github.com/lsst/obs_subaru/blob/master/python/lsst/obs/subaru/filterFraction.py) which would need to be modified to support physical filter names in addition to afw_names.
Most of the Stack code assumes that Filter::getName returns a band, so the new Exposure::getFilter should prefer the band as the name passed to the Filter constructor. The exceptions, which would need to be rewritten before
However, to make sure we haven't overlooked any cases, we should probably post a warning on CLO before merging.