Hi Guys,
Sorry I'm a bit late getting to the table on this one! Neat little setup btw, like the concept! I've been rather swamped recently with other things, but my mind is still working away on these N8X0 projects in the background ;o)
A few thoughts. First off, while a flexible cable that wraps around under the kickstand sounds cool in theory, it really would be quite impossible both due to the connector size itself, but more importantly the fact that once you plugged it in, if it was flush so that the kickstand would still close... that bad boy is NOT coming back out... which as cool as it would be is definitely not an acceptable way to go for most people! (Ever tried pulling on something that's connected just via a FFC? lol don't!).
As for the Pinouts in the battery compartment, as far as I know nobody's actually got around to confirming things... I've got all the parts to try it out, I'm just in the middle of moving and things right now so I haven't had a chance to. Basically on the N800 there are two sets of pads, one is definately the JTAG, the other is a set of 4 or 5 almost directly beside the USB port... which strangely enough, when you put the device into OTG Host mode, one of those pins goes to 5V+... and when in device mode, it sits at 0, so that's a pretty good indication that they at least have SOMETHING to do with USB... I've got the pogo pins to try it, but the problem I ran into was getting them aligned properly, determining the correct pinouts, and having them stay in place without building some kind of box that was twice the thickness of the N800 itself to attach to the back of it. Now, granted, if you're going for that whole "hard drive and USB hub and battery packs and....etcetc" you're going to end up with more of a "laptop to wrap around the N800/N810", so the size thing might now be an issue; If I can help out in any way let me know!

One other thing worth mentioning... You can now also get "360 degree" USB adapters that will let you plug things in backwards (i.e. a flash drive facing back beneath the tablet instead of straight out). I would love to be able to find one with a mini-port on one end to modify up (how sweet would that be?!?) but I think the chances of that are slim to non-existent right now; however coupled with the OTG adapter it would work, though still a bit bulky. I'll post up a pic of what I mean this evening if anyone's interested (the adapters are a bit pricy though, something like $10-12 I think).

Thanks,
-Rob