classic workbench has nothing to do with the 4gb problem. problems are : FastFileSystem, scsi.device of A600.
For FastFileSystem, there are two alternatives, use SmartFileSystem (only for 020), or FFS of OS 3.9.
For scsi device, you need patched scsi device. Not sure this is possible without softkicking (or a custom ROM). Which will lower your available RAM even more.
Classic workbench has nothing to do with these two, because it is based on OS 3.0/3.1.
But it is useful, for other purposes, yes.
