It'd have to come up as both a keyboard AND a gaming device to allow normal typing, OR it has to have a pretty complex driver.
It's pretty common for gaming peripherals to register themselves with the host PC as many different devices to support their various functions. For example, many gaming mice will also register as a keyboard so that buttons can be mapped to keyboard inputs. I had a mouse once that could present itself to the PC as a joystick if desired. And of course there's the NKRO trick where a keyboard will register itself as more than one keyboard.
I think that the trick, in the near term when there is no software written with analogue keyboards in mind, will be for the keyboard to have a number of different modes that the user can toggle between and/or use by holding modifiers. For example, there could be a regular keyboard mode, a gamepad emulation mode, joystick emulation mode, steering wheel + pedals emulation mode, intermittent mode (for games not designed for analogue inputs; basically, when holding a key down less than all the way, this mode would send repeated ultra-fast keypresses over and over; the further down the key is held, the less the interval between keypresses), and even mouse emulation, which I don't expect people to use for gaming but could be nice as an alternative to the TrackPoint for a pointing system that does not require the hand to be moved out of typing position.
I don't know enough about hardware design to say for sure what an analogue keyboard should do, but going by what I have seen from devices I've owned, the custom seems to be for the device to simply register itself as tons of different stuff, even if it's not using those features at the moment. So you'd plug in you Flaretech keyboard and it'd say to the PC, "Hi! I'm three keyboards, a mouse, a controller, a joystick, a steering wheel, and a set of foot pedals!"
