Your release notes says that the MK4 does not support male voices. But I tested this earlier (that was before your program was released, I send the command with I-Bus Analyzer) and GB male voice worked with my MK4. But I did not make a road trip and test if the soundfile actually is as complete as female voice. Filesizes are much smaller in male soundfiles vs. female soundfiles. Maybe you could still leave this option enabled for MK4 but with a warning/activation toggle.

Arrival time: is it always enabled with the MK4 or why it's not a valid setting for the MK4?