I'm reading all these, and I have mixed feelings about it. It's not exactly something that can be done. I mean, if you could sue a guy for making a clone, then Microsoft would have folded years ago under Apple's Lawsuit back in the early 90s/late 80s. Then again, most of the laws regarding software has changed since then, and now you can be sued for using a single line of code that is found in something proprietary, and vice versa. Unless the clone makers can make enough modifications to their versions to make it distinguishable from the Gateway, in features mainly, then they are blatantly ripping off someone elses work, and theoretically could be sued.
As for legality, sadly the Gateway was only made to play roms, not homebrew. If it had Homebrew capabilities, then I could see it falling into the category of Homebrew device, which is perfectly legal. But because it's only function is related directly to piracy, it can't be considered all that legal, and as such couldn't sue without getting in trouble with Nintendo. After all, if you try to sue someone claiming you should be the only person who can legally sell illegal merchandise, then you're painting a big, glowing, neon red target on your back for the companies you are essentially pirating from. So again, they could sue the cloner makers, but not without the big possibility of getting a target painted on their backs for Nintendo to zero in on.