Many projects benefit Wine indirectly—DXVK is of course one—but it would
not make sense for Wine to sponsor a GSoC project to work on, say,
GStreamer, or the Linux kernel.
IMO GStreamer or the kernel would be acceptable, if it's focused on something that wine needs. I.e. some new codec or a kernel feature that would benefit DRM, etc.
We did such a project a few years ago with GStreamer, though I wouldn't use the results from that project to influence the current discussion ;).