Moving files was not new, but the PCE was the first console to save to the system (that I can think of) and whatever they had then in 1987 they were stuck with forever. The Bank was years later and designed to reduce some of the headaches but it was still bound by the original design. It was also bound by old tools, a budget, and a release date. Home brewers have done much better, but they did it decades later with multitasking computers and emulators that don't require you burn a rom every time you change something.
The CD-system bios and the games themselves were able to recognize where individual save files started and stopped, so there shouldn't have been any formatting problems. Unless Hudson gave a deadline of "before lunch", whoever made the Tennokoe Bank should have been able to set up individual file copying with literally just a few more lines worth of code, especially if he never wasted time on the silly four-banks structure and just made it one big pot.
The problems caused by copying the entire internal memory are incredibly obvious. These guys worked on computers all day, and yet they screwed up what is essentially a copy/paste tool with the most basic possible GUI. First of its kind or not, that's inexcusable IMHO. This was the same company that made an operating system for the X68000 in 1986, for crying out loud.
IN DEFENSE OF TENNOKOE BANK
(1) I think you are overlooking an important factor: ease of use for all consumers, including average/dumbass/child.
For mainstream consumer goods, it's much better to design a system that a dumbass/child can understand.
(2) Copying en masse = dead simple, fast, efficient and the operation you are performing is immediately obvious. Period.
Engineers and average users know that the contents of a bank will *always* fit when swapped back and forth between HuCARD and real hardware—dead simple conceptually and in actuality.
No prompts/messages warning about files/banks being "too large" to move/transfer.
(3) I can't help but think that engineers/designers were not just worried about users *actually* losing data...but also with users *seemingly* losing (or losing track of) data. Manually managing files is tedious, boring, annoying and potentially quite messy, confusing. You can lose track of stuff. Users will absolutely do silly things when (a) given full access and (b) system allows for flexibility/complexity. Allowing users to f*ck things up only frustrates the customer (the *last* thing Hudson/NEC want to do).
(4) I don't disagree with you: Hudson *should* have included advanced file management tools for the "power user", but these advanced tools should have been "hidden" from the average dumbass/child. It's OK if most folks never used the advanced tools.
ASIDE: If file management with mouse+keyboard still sucks today on modern PC OS (and we have benefit of modifier keys to select multiple files at once), individual file management would be cumbersome on PCE with controller, menus, message boxes, etc. Every operation would take many steps and require many confirmations. And you would grow numb to warnings from the incessant dialog boxes.
FURTHER THOUGHTS...
The design decisions to deliberately limit how a user manipulates/manages files has interesting implications:
(a) "Bank" as a metaphor for time. I can't help but love thinking about how a "bank" can represent an era of time (what *constellation*—group— of games was I playing two years ago?) It's a nice *group* snapshot of a time period.
(b) "Bank" as a metaphor for "comrade"...this is when you help out/play with a friend/family member (especially when they have their own console, separate from yours). When you copy/swap files, you are capturing a unique piece of their gaming life. Again, it might not actually be a snapshot of a single person's gaming life...but rather *every person* who uses the damn console (siblings, parents, yakuza, etc.)
(c) "Bank" births a new Prank. Are there any anecdotes about people pulling pranks on unsuspecting family/friends by "deleting" save files?