This summer, I'm working on my own version of the Trezor One DIY. I've redesigned the board to include a USB-C port and a larger 1.3" screen (although not visible in this photo, the one shown in the photo was taken from an Amazon breakout module and it's 0.95", the same as Trezor One). All the components are situated behind the screen, and I would say the result is a similar size but with a different appearance.
Cool project, but I would love to see someone doing something similar for Trezor Model T, or adding different chips that has larger memory than in Trezor One.
I think microcontroller used in Trezor One is STM32F2 and in Trezor model T it's STM32F4, that is small change but it makes a big difference with RAM and Flash.
Bigger screen and usb type-c supporting is nice to have, but beware that Trezor announced they will stop manufacturing model One soon, that usually means less updates and bug fixes in future.
I've tried compiling the firmware and the bootloader with PRODUCTION=0 and MEMORY_PROTECT=0 just for the sake of having a non-production Trezor, and compiling is easy, but I'm stuck in the process of signing the bootloader and making the firmware accept the bootloader and such.
How did you fix this, and did you talk with Trezor team about your DIY device?
I would like to see refreshed Trezor One device, maybe renamed to something like Trezor 1.1 or Trezor 2