The ratios still apply regardless of how big you want to make the space. Since this isn’t going to be dedicated, which you’re alluding to it being multipurpose, work the ratios the best you can based on what you want to do with it. Most people who strive for a “great sounding room” rarely get it. They end up over-damped and dead sounding or there’s not enough damping and things are too reflective with more modern hard surfaces. Odd walls and dimensions can help break things up and with furniture, rugs, carpet, wall hangings, there’s a lot that can help. This is an area that can easily be overthought.
https://www.stereophile.com/content/listening-room-forgotten-factor-page-2
https://audiophilereview.com/room-acoustics/ideal-room-size-dimensions-and-ratios-for-audiophile-listening.html
https://www.psaudio.com/pauls-posts/critical-room-dimensions/
https://www.stereophile.com/content/listening-room-forgotten-factor-page-2
https://audiophilereview.com/room-acoustics/ideal-room-size-dimensions-and-ratios-for-audiophile-listening.html
https://www.psaudio.com/pauls-posts/critical-room-dimensions/