The spinner would only work for the MAME beatmanias, but the only circuitry I know of to change optical encoder input into pulses for the PS2 controller is inside the official Konami controller (and the Rave Discman, which is horrible on its own but a good choice for the core of a homemade controller).
The Konami official controller can be had for $116 at Lik-Sang ($36 shipping to California) and is high-quality, long-lasting, and neglibibly different from the arcade except for the most dedicated of players who pay hundreds for the Konami "Arcade Style" controller or a homemade one. The keys required are very specific (poker buttons aren't good enough, I've heard) and quite expensive, so I'd recommend the Konami official controller, and a PSX - USB converter if you want to play the MAME beatmanias. I've done this and it works fine with any converter, even the ones not compatible with DDR, because there's no double-axis-pressing (if you don't know what I mean don't worry about it.)