Extension request: control of provoking vertex

Given that VK_EXT_transform_feedback exists, I think having control over the provoking vertex for flat shading is also called for. Indeed, the provoking vertex convention in OpenGL ES 3.0 and 3.1 is not settable and is the last-vertex (instead of the first as the current Vulkan spec). Given that mobile GPU’s support GLES 3.0 (atleast, and often GLES 3.2) and that desktop hardware support GL 4.x, I suspect that all GPU’s on the market have the ability to have the provoking vertex as the last element.