It's not
that hard to make occupied lots safe to use.
Instructions for safely saving sims on Lots, for use in other hoods:
1, Package them on their lot.
2, install them into the throw away hood using clean installer (making sure you only install the family and the lot - no one that isn't living on the lot)
3, use Simpe or Pescado's Lot debugger (ffsdebugger) to clean up their memories (or use both).
4, re-package them on their lot.
5, install in your new hood.
simpe
http://sims.ambertation.de/clean installer
http://sims2pack.modthesims2.com/