If the OpenMoko people were able to do it, what's stopping Maemo.org from doing it too?
I propose an jumbo sized OMAP4 device with 2 SD slots, 2GB of LPDDR2 RAM (not on the SoC) , replaceable camera modules, replaceable GPS modules, and replaceable basebands. (USB 3G dongles?) It should also have its own USB3-A female connectors on the side, a micro-AB port for charging/data and a really, really big battery pack.

C'mon TMO, time to make that 6-inch whopper!