I've done some testing on my own server, and I've found this to be the most reliable method for making an area into a Sanctuary (for a mall or other special purpose).
1. visit the area in-game and use the .gps command. This will show you the AreaID.
2. open up player.cpp (found in /source/game/player.cpp
3. Search for this line:
if(zone->flags & AREA_FLAG_SANCTUARY) // in sanctuary
4. Replace it with this line:
if((zone->flags & AREA_FLAG_SANCTUARY) || (GetAreaId() == 2477)) // in sanctuary
Just replace "2477" with the area you want to be a sanctuary. If you want more than one area, just add them in like this:
if((zone->flags & AREA_FLAG_SANCTUARY) || (GetAreaId() == 2477) || (GetAreaId() == 1234)) // in sanctuary
And so on. No illegal editing of DBC files needed
I understand this is probably simple for most of you, but I wanted to post it for posterity in case I need it again and forget how to do it.