Yes, unfortunately the EXT Cartridge board would have to be significantly redesigned if all the chips for all the functionality would even fit, and even then it’s not compatible with the original cartridges. You are totally right with the measurements, the edge connector would not fit a uConsole 
It would be feasible tough to design specialized EXT boards, like one to pass through the IO from the PCIe connector or Ethernet with serial.
With this project I got enough on my plate and didn’t pre-order the uConsole anyhow, so that is up for the community to make. I already saw some neat progress on some modules, notably LoRa and GPS.
Regarding updates, I’m finishing up on the daemon to detect cartridges and do all the (de)initialization for plug and play. I’m developing it for yatli’s Archlinux branch in mind, it should be possible to compile it for other distros like Armbian but I haven’t tested anything yet. Next up are manuals, I’m sure one has to be included but I could be wrong.
News from PCBWay is that the EXT boards are done, and the printer boards are finishing up. Tough I made some mistakes with the BOM and I’d have to solder a significant number of parts manually. It’s the quartz for the USB hub chip and all electrostatic protection TVS diodes. This plus I opted to solder all through hole components myself, especially the edge connector, to keep cost down. Also the dual ethernet and serial cartridges have some errors too which need a little touch up.
This and all that means it’s that, if I’m fast with all the remaining tasks, in a month or so I’ll have all the products available on Tindie hardware wise. For the software there’s still a lot to be done that I haven’t figured out yet, like hosting the package manager repository.