The beauty, as well as the challenge, of HBD is that everybody starts out on an even playing field of $185m every season. It's what you do with your $185m, i.e. how wisely your allocate and spend your money, that makes the difference.
I'll use my team in Cooperstown as a perfect example of why this suggestion is not a very good idea. I built a very good team over a number of seasons via good trades for young prospects, a few key IFA signings, and some very good drafting. I was also pretty lucky, particularly with the draft, because I was able to get the right mix of quality draftees at different positions over five seasons or so that all fit very well into a final picture. Six straight division titles and two World Series appearances (unfortunately, back-to-back Game 7 losses) in what is generally considered as one of the most (if not THE most) competitive HBD world was the high point of my rebuild.
Then my guys started hitting arb and FA. Tied to a $185m budget, I had to make decisions that I knew would have negative impact in the long term. I cut down on my draft scouting budgets. I cut down on my IFA budget. I cut down some on medical and training. All because I needed to find a way to meet increasing payroll. I knew this was where I was going to end up many seasons before. It was part of the business of building the team that I built in the manner that I built it.
With a performanced based budget, under this suggestion, I would have gone up to $200m per season. That would have made it a LOT easier to keep my team together, and I wouldn't have had to make some of the decisions that I made. Which, though "hooray for me", would have taken some of the challenge away from the game.
As Mike said, "the rich get richer". Really not a good thing for competitive balance in a world.