Workbench.library AFAIK is only used for Workbench and not Games/Demos etc.
Since booting workbench means... using a floppy disk or hard disk... I don't see anything wrong by loading the workbench.library from the LIBS: folder of an hard disk or floppy disk accordingly 
Nice list.
BTW, the 4000T did just that to fit IDE and SCSI drivers in Kickstart ROM, so I'd say it's a perfectly viable option.
