I see on TERES-PCB1-A64-MAIN you have a currently unused connector carrying such important interfaces as usb-otg, uart, i2c, spi ... no idea what your plans are with this (or if this is just for testing after manufactoring), but what I'd like to see:
Some new variant of TERES-PCB2-IO (lets call it TERES-PCB2-EXT) which in place of the usb connector has a docking connector (much more lines on the same physical dimensions). And an external board (let's call it TERES-EXT) with the matching docking connector (maybe on short cable) making all the lines available in nice standard connectors.
TERES-EXT would have at least usb-otg and UEXT and a case robust enough for field usage. Also maybe some extra GPIO lines or whatever you can fit through the physical size of the USB connector. (Personally I wouldn't mind slightly enlarging the hole in the case to allow for an even bigger docking connector).
What do you think?