There is a lot to be said for this theory. Of course a better funded team is going to hire better riders. But, personality stars like Peter Sagan will always shine on their own.
The idea of salary capping might make reasonable debate, but I suspect the UCI is run much the same as the IOC and it would take some influential people like Merckx, LeMond and maybe Phil Liggett to move the conversation to a public discourse.
The biggest thing that might happen to trigger a financial cap is the fact that the local French Teams and Riders are not doing very well. Bernard Hinault has given up and is fully retiring this year back to his farm in Normandy. He was the last French winner back in 1985 (5th win) with a little controversy about teammate Greg LeMond being held back to ‘allow’ Hinault’s win.
This year, 2016, French riders won only a single stage (19) even though that rider ended up as #2 for the Yellow Jersey, Romain Bardet. This is with 5 France-based teams and 37 French riders (both being the most of any nation.)
So, my guess is that the ASO, the race organizers, being French themselves, might look at a financial cap just in the hopes that their home guys might have a better chance after 31 years. How that will work out with the UCI, as the international professional bike racing controllers, is likely beyond my pay grade!
My $0.02 worth!