I'm not sure Raspberry-Pi is the right device to use for this.
It isn't; it's way too much machine, unless you're talking about something like a Pico, and even then I suspect it's too much, although at $10 why the hell not. You could probably get away with something ESP32-based considering you're effectively talking about controlling either a) a series of 35-light long LED strips (and white LEDs would be plenty bright even with 3D-printed diffusers in front of them) or one single strip that is 35 x (however many digits you want it to be) lights long that you would need to inject power into at intervals. (If I can run a 6,144 light matrix (really three 2,048 strips, effectively) off of one ESP32, an eggcrate should be no problem.)