I knew it, people made DIY disc changers! you could do this with blu ray too, all using just 1 drive, but the skills needed are beyond my own
https://hackaday.com/2011/10/18/a-cd-ch ... e-of-wood/
http://hackalizer.com/jack-the-ripper-i ... c-changer/
https://mniec.wordpress.com/2011/08/22/diy-cd-changer/
https://www.eeweb.com/homemade-cd-changer-robot/