I'm rather skeptical about the idea of PCB-mounted keyboards...
I mean, even if you can get decent switch stability with a metal case, do you really want there to be nothing between dust/crumbs/stray drops of coffee and the PCB? Just imagine all that crud that usually accumulates on the plate of a keyboard over time accumulating directly on the keyboard's electronics instead. And what about absorbing shocks from bottoming out, or if you accidentally drop a book or something else heavy on the keyboard?
Personally, I like my keyboards not only with a plate, but with that plate being as thick as the switches can support and made out of something nice and tough (like steel). Sometimes I do wonder about unexplored "third options", like having a piece that goes where the plate goes, with bits that come up and cover the switches (like an Azio Mech4/5's plate), but to which the switches don't actually click. With something like that, once you undo all the screws, take off all the keycaps, and open the keyboard up, you could simply remove it-- not only allowing you easy access to switches, but also making it very easy to clean. At the same time, it'd protect the electronics from dirt and liquids, and might even help absorb shocks (if the keycaps hit it when bottoming out). Of course, you'd still need to use PCB-mount switches and support the PCB to the same degree as with any other PCB-mount board, but the combination of easy switch replacement, easy cleaning, and decent protection might make for a decent long-life product. Until something like that exists, though, I'll take a plate.
