You know you can create an external audio track, right?
If you use a player like MPV or something like it, it will load by default the external audio file with the same base name (except the extension). For instance, if you have a video named Famous.Movie.2024.x264.AAC-GroupName.mp4 and an audio track in a file named Famous.Movie.2024.x264.AAC-GroupName.m4a, MPV will load that external audio and you will be able to seed the original file without need to remux the video and the new audio into a new file. This way you will save a lot of space.