Different quality asset bundles for multi platform game

I have a game which needs to run on iPad2 and iPad3. The first few levels will be included in the build, however the other scenes will be downloaded through asset bundles.

My goal is to have bundled scenes for each platform quality. E.g Level5_HD and Level5_SD so iPad2 users downloads the SD which is smaller and requires less memory.

Is there any way on how you can build asset bundles for different platforms?

E.g. If I reference an HD texture in a scene, this will be included in the scene bundle which is OK for the HD_bundle but how can I then build the SD bundle?

Thanks in advance.