I'm more than happy to have to go through my own routes, individually move routes 10% above default, or 20% below, or whatever. All I want is that I not lose all my changes whenever I reset prices to default. Either by having a feature that lets me click 'reset all prices based on current default' that keeps the percentage difference I've already set, or by having the default price for a set route displayed somewhere, in the same way the current global fuel price or interest rate are displayed. Default has gone up 5% since I last checked, then ok, I'll increase all prices by 5%. Can use that as a workaround now, by looking at a route you know has been left at default, and resetting just that route to see the % change.
Not a fan of more automated system, that will do the work of looking through your routes for you.