So what about a widescreen option for the other USB loaders, GX and CFG?
And about the PSX USB adapter, I actually own one for DDR mats (don't actually own any PSX pads however). It's not the same model, but it is EXTREMELY similar to the one on Amazon - heck the shape of the device is exactly the same (the color and labeling are different however). I'll definitely test that out today...
I also own a classic controller to USB adapter. I think I'll try that too for lulz.
EDIT:
That URL has hotlink issues, so I re-uploaded said image to imgur:
http://i.imgur.com/uUdDLwW.jpg
EDIT 2: Nope, neither USB adapter of mine worked. Man, I really wanted to play F-Zero GX with a DDR pad too!

(no seriously, I did) For reference, the USB adapters are these:
PSX:
http://www.mayflash.com/?Products/PCUSB/PC038.html
Wii:
http://www.mayflash.com/?Products/PCUSB/PC052.html
EDIT 3: I'm a noodle, I just realized that I ONLY tested in the sample loader. Never crossed my mind that they could work in-game and NOT on the loader. Also I forgot to test with every controller & USB port arrangement possible.
EDIT 4:
Is that not just a Mayflash Super Dual Box but with generic branding?:
http://www.mayflash.com/?Products/PCUSB/PC016.html
EDIT 5: Uhhh... not only could I not get my Super Dual Box Pro to work, but I can't even get a normal USB keyboard to work (even though it works on the Internet Channel). I even tried hitting ctrl+alt+tab but it still didn't do anything (though the num/caps/scroll lock lights would toggle on & off so it was connected fine).