Beautiful! Love the early E24.
For a radio refresh, try the Blaupunkt SQR46 DAB. Looks exactly like the late 80s Blaupunkts, is shallow enough to flush mount, and supports BT audio & RCA outputs if you want to add an external amp.
Here’s it in my E31 (the iPhone flash makes the screen look a lot more dim than it is. It’s the same brightness as the OBC in real life):