I think that is a great idea. You can buy Bluetooth stereos for well under $100. I’m surprised that more people don’t do this. It would actually be kind of “period correct” as I had an 8 track player under the seat back in the day. My dash was already cut up, so I just did a dash mount. I was going to Velcro the remote to the steering wheel and have radio controls on the wheel like my other cars, but the remote is infrared and has to be pointed at the radio to work. If the remote was RF rather than infrared, that would work for a radio under the seat too. Mine is a daily, so I love the modern radio!