In AutoCAD 2006 you can now Offset to a current layer. In the Offset command prompt there is a new option to set the offset to be on the current layer rather than the same layer as the entity being offset.
Current settings: Erase source=No Layer=Current OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <1.0000>:
An example of how this could be used. If you have one layer for interior walls and one for exterior walls. When you wanted to offset the interior wall for the exterior wall, you could have the exterior wall layer current and the offset line would be placed on that layer instead of the same interior wall layer.