If you can make guarantees about it not having latency issues, you've definitely got something there I'd consider interesting.
With the relative lack of Adaptoids out there, how about N64 support? There's also always Genesis, Saturn, Dreamcast-- lots of other systems where you end up with a boatload of specialized adaptors for everything to play stuff on your PC.
Also, if you can get true button pressure sensitivity on PS2 controllers, you may have the holy grail for PS2 emulation. You may have to seperate one PS2 controller off into multiple devices to get enough axes on Windows-- a PS3 controller is the current best choice, but those triggers aren't so hot for some games (e.g. Gradius 5-- I use R1 for powerup and R2 for option control.)
I'd honestly be willing to pay up to $80 for a solid converter that just does *everything* cleanly and doesn't need me plugging and unplugging adaptors all the time. I say this because I was actually thinking about gutting a USB hub (and various adaptors) and building something like this.