Indeed it is. And I partly agree with knc1 about nearly all things already present. However, with USB OTG the important bit is - besides of course a HCI (host controller interface) - the correct switching logic. I short skimming through the kernel source seems to indicate that some (probably untested) support is already in place.
Also, Hardware will play a role. While the data lines might be driven by a charge pump on 5V levels, I doubt so for the VCC line. But then, this is highly untested grounds. A USB hub (self-powered) might rectify the voltage/current parts here, as was mentioned in this thread before.
However, it's not just some end-user config option in the kernel, I think. That's also due to the platform: The kernel was patched to fit it and when patching a kernel to fit a platform like the Kindle, it is highly uncommon to bring in more - including more options - than the developers need to. Unfortunately.