@Nivi Mandappa Apart from all the great points mentioned here, when I was an HRBP, one area where I felt heavy pushback while suggesting a salary restructuring was "Why is it necessary?"
Data points to consider over here are (you might have done them already):
Rate of attrition - if there's a visible spike with tangible evidence of people leaving for higher pay, your case becomes easier
Comparison with P50 like @Chetna Gogia mentioned
Impact of people leaving - certain business leaders immediately get it when you show them an apple to apple comparison (in this case impact of new salaries visavis revenue or any other metric)