The current setting, as I see now, is correct for dense populated areas, big cities etc.
I was thinking in the first place more about something like a new set of tags in the settings.xml.
Maybe like "first visible zoom level" for each type of roads.
Something for advanced users, who would play arround, search for a trade-off between visibility, separability and speed and then give a feedback, before implementing it in menus as @ahr said.
@hurdygurdyman: A new settings menu is in fact something for the wish list, as you said, but not only as priority for Androids - it would be something for all versions.
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