Mixed manual and auto routing

I have a mixed-signal design requiring me to manually route traces for RF (VHF) as striplines and to do some rather careful power supply routing.  Separately, most of the rest of the design is less critical and I'd prefer to auto-route those portions.  The manual routing, including the creation of the striplines, takes hours.  This portion of the design is relatively stable, so I'd like to do the manual routing once and leave it untouched as the rest of the design evolves.

I'd like to be able to freely use the autorouter and ripup tools but leave the manually-routed traces alone.  I have tried to do this with various techniques such as

• Putting the manual traces on "new" layers that the autorouter does not know about and then merging these into the real copper layers at CAM time.  This requires great care in using restrictions to keep the autorouter from using the space on the board reserved for these manual routes.  In practice, this can only be done if the manual and auto traces are on completely separate sections of the board.  They are not.  The assisted manual router also does not know about these "new" layers, so this trick requires some sort of routing using the real layers and then moving the resulting routes to the new layers.  Also, DRC does not pay attention to these new layers and I can easily create a problem that DRC misses.  I don't view this as viable.
• Doing the manual routing normally and then saving the board and schematic files as "golden" files.  I then continue doing the auto-routing, but instead of using ripup to go back, I do some fiddling around with deleting files and reverting to the golden files.  This is clumsy because the Eagle project file tracks backup versions and does not (appear to) support this kind of file fiddling.  Such fiddling usually leads me to getting the board and the schematic out of sync or otherwies confusing Eagle.  The bigger problem is that when I have to revert, I lose any subsequent changes I'd made to the schematic.  This is not a viable approach either.

The real need is to be able to mark the manually routed traces in some way such that the ripup command can be instructed to ignore them.  Is there some way to define an attribute, a group, or a class that I can use with the manual routes that ripup will recognize and ignore?

Thanks.