After the Maker Faire, I went back to the Graupner mc-17 remote control.
The Arduino library from tronixstuff for the KTM-S1201 LCD which is also using a mPD7225 controller was a good starting point. But to get the LCD up and running, it took quite a bit of fiddling and logic sniffing.
Once the controller allowed me to switch on individual segments of the LCD, I needed to adapt my implementation to this specific display, as it offers remote control specific elements unusual for normal LCDs. With a proper mapping of bits and bytes to their respective LCD elements, it was easy to implement the usual alpha-numerical characters. Each of the digits is controlled by a word / two bytes. For each byte, one bit is used to control one of the additional symbols like colons, dots, or remote controls specific texts.