I may be wrong, but I posit that 15d6 SA is a) not that easy to achieve, and b) not that
useful on RoT in and of itself. All classes which progress sneak dice do so at 1d6 per 2 levels or worse (though you can squeeze in an extra 1d6 here and there with good splits, you often pay a BAB penalty for doing so). Rogues are dearly in need of Epic feats (Epic Precision, Epic Prowess, Expose Weakness, PTWF, and either Epic Dodge or worse, Self-Conceal, or yet worse: both). So Improved Sneak Attack has a steep cost (and requires 8d6 to qualify, anyway, which is non-trivial). The Kaedrin feats help Scout and Swashbuckler, not exactly super-popular classes, but not Ranger (1d6 per 4 levels is too slow to get to 15d6 by level 30, and they qualify for Epic Craftsman already anyway). Neither my Scout/Ranger build nor my Swashbuckler build would qualify to wear arbitrary class-restricted gear under this scheme (nor under your scheme), and would have to give up a lot to do so. The Swashbuckler comes close at 12d6, but she is really
So where's the cheese?