I get the impression, reading around, that a central AC can't dehumidify
without cooling, because the condenser, which is what would heat
the air in a dehumidifier, is outside, being cooled by outside air.
It should be possible to expose the condenser to outside air or
to the inside air, depending on whether you want just dehumidification,
which would heat the air, or air conditioning. So I don't know why a
central AC couldn't also be a dehumidifier. It would have to have a
humidity sensor of course. For my purposes it'd have to be able to reduce
the humidity to 50%.