Saving a copy of an assembly with selected parts and drawings renamed

I have an assembly, named ERU3, which has sub-assemblies and sub-sub-assemblies. Some of the sub-assemblies and parts are generic parts used in other assemblies, and some (those prefixed with ERU3) are specific to the ERU3 assembly. Some of the ERU3 parts have drawings.

What I need to do, and what I'm having difficulty figuring out a simple way of achieving, is the following:

I want to save a copy of the assembly as ERU2, and copy any specific parts and sub-assemblies (changing the prefixes from ERU3 to ERU2), and also copy any drawings (again changing the prefixes to ERU2). So that I can then make changes to the ERU2 parts, having them update in the ERU2 main assembly, but leaving the original ERU3 assembly, parts and drawings completely alone.

I have tried the Save as copy option, and using the Advanced button I can use find/replace on the filenames. This seems to do everything I want except for making copies of associated drawings, and there are about 40 such drawings, so I'd like to copy them to the new assembly if at all possible.

I'd welcome any any ideas

Thanks in advance, Elliott

SolidworksAssemblies