However, we're in agreement. There seems to be little reason to have a case which cannot accommodate the PSU to be an internal component and allow for proper rail mounting and max density. If anything, I'd put this in the category of making things more difficult for KNC to sell to massive operations - it's annoying, but not necessarily a deal breaker. Maybe there's some other reason that I can't think of why they'd design the case as such - beats me though.
There are good reasons not to have an internal PSU, additional expense, more heat to get rid off, and there is no problem convincing customs that it's not a mains power device that requires certification. If you need other cases, have them made and perhaps sell them on eBay as well. All the BFL models except the 500GH/s use external power supplies.