I’m sure some enterprising designer could engineer a set of smooth metal tines that had the same, if not better, friction characteristics as plastic for the starburst pads. This, of course, assumes that starburst pads are the only style of pads that could work well for 2A, which I’m still skeptical about.
But ultimately it seems to me this is less of a design/engineering/manufacturing problem and more of an issue of “why bother?” 2A just doesn’t seem “big” enough (market-wise) to drive the development of metal alternatives, and without a big push in R&D, not enough prototypes will emerge to show their potential for 2A.
So I guess the real answer may be that there’s simply not enough marketplace demand to push the 2A envelope in terms of yoyo development–metal yoyo development in particular–any further than the current status quo. Coupled with the prevailing belief that we’ve achieved the absolute pinnacle of looping yoyo design with the ProYo shape, made out of plastic, featuring starburst response pads, and produced with flawless manufacturing. The only thing that seems to differentiate brands and/or models is color and graphics.