In the UK, at least, since the majority of routes are likely to be North/South, I think a GC option would be of limited value and I personally, don't see the need for it. However, I can understand only too well, the desire of others to have this option, so, how about:-
1. Show one or the other – user selectable option in Settings, but default should be RL;
2. When selected, show the RL route in magenta, as currently;
3. When selected, show the GC route in blue;
I know that displaying a route line in a colour other than magenta it is a radical departure from the norm, but at least there could be no mistaking which is being displayed.
Tim – In the case of someone loading a route created by another, would it be possible to check each user's setting and convert the downloaded route if necessary, or would this just be a coding nightmare?
Nexus 7 (2013) – Android 6.0.1 & SD 188.8.131.52373
Huawei P30 – Android 9.1.0 & SD 184.108.40.206373
PC – Windows 10 (Home Ed) Version 1903, Build 18362.239 & SD 220.127.116.11