At a prior job, we occasionally updated the global functions, as well. If I recall, we PERFORMed the program with the functions. Whenever we set the functions, we also set a couple of global variables to the program's creation date/time, so we only reset them if the program was updated.
There was no need to DROP or ADDR, as PxPlus dealt with that automatically. The new versions of the functions would take effect immediately upon return to the caller.
Caveat: We were using Linux, not Windows, for our server. I don't think it should make a difference, though. Then again, it's Windows...