You'd have to implement directplay all over again, and MS hasn't released any information as to how it works.
The very simplest approach is to take a directx capable wine (ie: TransGaming's WineX on sourceforge) and to add the missing parts to allow directplay4 code (not dplay8) to function within it. The sources are available, and I am sure TransGaming would accept contributions in their matter.
.. After all, I'm their sysadmin (currently on leave, and soon to be on parental leave).
-- Luc