Erm, where do I start?
BOOPSI is a runtime classes API for Intuition, it has nothing whatsoever to do with "loading libs and drivers".
Kind of. BOOPSI actually started as a third party student project. It got imported into CBM and distributed as a Dev tool. Officially at 2.0, but really a lot earlier than that.
And you are both correct, the limit on using the technique is which exec and intuition library is present at system boot. Those are the 2 you can't mess with by straight replacement, so I've been told.
I'm just amazed I didn't know. I thought it was a hack technique. Seems like that is what CBM where aiming for all along. Or rather, the Amiga implementation of the original TripOS libraries and device core system. (TripOS looks spookily the same in spec, and is still being supported as a commercial product).
If you look down the list, you'll see mentions of the common "you must replace with a later version" problem files - scsi.device, filesystems, Picasso96, Cyber, etc etc.