Although I don't exactly like how this was implemented (it seems hardcoded judging by what messages are brought up when you don't have the model pack), I get an error message with the Heretic model pack installed.
From the log file:
Log: THE DOCKS
Dev: Client level loaded
Log: Can't find models/weapon/g_skull.md2
Dev: 173 subdivides
Dev: 176 seg subdivides
Dev: 26k light mem
According to the Heretic models directory structure, it should be looking in the "weapons" folder instead of "weapon"...