I have an original Nostromo N52, back from when Belkin still made them, and it is quite comfortable. I just wish it was mechanical. I just had the chance to see the Tartarus the other day, and I have to say, the quality seems to be crap. The original was fairly well constructed, and the Tartarus feels like cheap crap in comparison. I know the n52TE, or what ever, that Razor released after taking over the Nostromo from Belkin had more problems than the original, largely with software and firmware. The thing that disappointed me the most was the thumb key and how flimsy it felt. It seems like the Orbweaver has a similar style key, which makes me worry about it.
The keypad is kind of a niche market, and with Razor leading the charge, I don't think it is one that will really improve any time soon. I see people going nuts for razor all the time, but I've yet to see a single product from them that really seems worth a damn. Quality always seems a bit on the low side, despite the high prices.
Using an ergodox as a basis would be a good start. To get the tilt going just really would need to put the slant on the bottom part of the housing. I'd shave a couple colums off as well, and reduce the number of keys near the thumb as well, to make room for a dpad. Scroll wheel doesn't seem like it would be that terribly useful (I never use the one on my n52, because it is in a bit more awkward place for me, and I have one on my mouse)