gst-plugins-ugly support in flatpak Bottles

[taoky]

Recently I tried to play a game with Bottles (installed from FlatHub), and the winegstreamer complains about missing decoder:

winegstreamer error: decodebin0: Your GStreamer installation is missing a plug-in.
winegstreamer error: decodebin0: ../gst/playback/gstdecodebin2.c(4719): gst_decode_bin_expose (): /GstBin:bin0/GstDecodeBin:decodebin0:
no suitable plugins found:
Missing decoder: Advanced Streaming Format (ASF) (video/x-ms-asf)

winegstreamer error: decodebin1: Your GStreamer installation is missing a plug-in.
winegstreamer error: decodebin1: ../gst/playback/gstdecodebin2.c(4719): gst_decode_bin_expose (): /GstBin:bin1/GstDecodeBin:decodebin1:
no suitable plugins found:
Missing decoder: Advanced Streaming Format (ASF) (video/x-ms-asf)

Although I could still play the game without video playback, it could be a problem for some games. As far as I know, the decoder of video/x-ms-asf (libgstasf.so) is contained in gst-plugins-ugly (which may bring some legal trouble in some regions?). However, it would be very difficult for end-user to install that in GNOME flatpak runtime. The current runtime contains gst-libav, gst-plugins-bad, gst-plugins-good and gst-plugins-base (https://gitlab.gnome.org/GNOME/gnome-build-meta/-/tree/master/elements/sdk), but sadly I cannot find a place where I can get gst-plugins-ugly into the runtime.

I'm wondering if it is possible for Bottles to pack gst-plugins-ugly as optional "Dependencies" (or by "Extensions")? And if not, I think that it would be convenient to provide some guidance in docs about alternative solutions about video playback in Bottles (use quartz and disable winegstreamer, etc.)

Thanks.