I wouldn't be suprised if Jens has already designed this board to fit into a standard, widely available electronics project kit plastic case. There are a ton of designs. Jens isn't stupid, so I'm sure he's thought of that.
It isn't a case of Jens being stupid, it is more Jens realises that some people want to make their own cases and gripe about the ones supplied. Of course the opposite is that those of us who want a case gripe about there not being one.

The MMC Replay came without a case, but fortunately it fitted into an easy to obtain C64 cartridge case and (with the help of a dremel) could be quickly installed. The C-One came without a case (insert in the PC case of your choice, just don't expect easy access to the ports).
I can't imagine anyone wanting to have one of these attached to their A500 without a case, but then I've been using my FPGA Arcade without on for over a year (I've learned to be very careful with my drink cups).