One of the news sites said it would ship in a sandwich case, although I haven't seen anything from Jens so far.
There are mounting holes, so a case should be doable.
However I can completely understand if Jens doesn't produce a case. People who aren't going to use an accelerator will probably want a small case, while those who plug an accelerator in the back will want a larger one. But how large? As the user may want to plug in an accelerator that doesn't even fit in an A1200 trapdoor.
He is on a hiding to nothing with this product.
jens tries a modular design, but it seems a bit of mistake. more disadvantages as the opposite i fear. seems many existing accels you may want to stick upon aca500 are not supposed to work. and also the case design and size are hard to decide. from what ive gathered in the a1k thread jens want to secure the accel with an iron plate, which you probably refer to as "sandwich". thats how i understand it at least.
edit: im sorry that it turns out like that. i was actually always in favour of modularity, but in this case it just doesnt seem to be worth the effort. id value it if jens turned to more ambitious tasks, but its apparently not his intention. lets face it the commercial (amiga) hardware market seems to dry out, still the fan projects may substitute it.