Although the IETF standardization of Vavailability is not completed, that work is expected to start in the near future. The justification for a separate package was the the underlying RFC may change during the IETF process.
An updated PIM with updated Vavailability is not a major problem for users of the model. Also, the Vavailability package references things in the PIM package and vice versa.
So for simplicity of defining PSMs, merge the two packages into one.