Essentially, the request is the equivalent of Toggle Note-Attack for the DMC.
My issue comes with a tiny-looped sample I use for a Drum-Kick. Like the Triangle, I can sweep the pitch down rapidly, though its by changing the sample rate every frame, rather than the Triangle's period. Only problem is, setting a new Initial Value every frame causes lots of unnecessary popping.
While that use-case is pretty niche, it seems like it would be simple to implement. (Though granted, I only have experience with small projects.)
There is an alternative that I suspect would be harder to implement, but would be more usefull: The ability to specify the sample's rate every frame so the sample itself doesn't end up getting restarted every-frame. (Or a Toggle Slide-Note to achieve the same idea.)