An extreme example using possibly the greatest ever football manager. I could give far more examples of players being the more important ones to a club than the manager. Bale more important than all the Spurs managers he played under. Suarez more important than Brenda. Ronaldo more important than Ancelotti. Messi more important than Luis Enrique. Ibrahimovic more important than Blanc. Aguero and Kompany more important than Pellegrini. There are more top class players on the planet than top class managers. Ergo at quite a few clubs there will be individuals who are better at football than the manager is at managing. Therefore a blanket rule that managers should get paid more regardless is nonsensical.
A flat wage structure does not work - see Arsenal as an example. If you pay the MD & the cleaner the same wage, there's no incentive. People in a capitalist society are motivated by money, it's bred into them. Do I work hard to move to the next level and earn more? Yes. If I were paid the same as the guy at the next level, my motivation would decrease. Same in football. If you want players who play for the shirt, play local lads. Everyone else sees it as a job.
I'm not advocating a flat wage where the cleaner gets paid the same as the MD. I'm advocating a wage structure where players are paid on an even footing depending on age, experience etc. You can still build in bonuses for apps, goals, trophies, improved with number of years spent at club, things like that. You could even have a range of salaries within each strata. I think there needs to be a wage cap also. Money dominates the game and there's a huge disparity between the big spenders and the have nots and the gap is widening because of the £300-350k per week deals that Utd have with players like Falcao and Rooney.