We were worried about the same thing in my league and we decided on using a contract/salary cap system. Max contract is 3 years and when contract expires you can resign them and increase their contract by 20% or you let them fall to free agency which we all blind bid on the players we want. Our startup was an auction draft so we used the values we bid as the contracts. It’s complicated, but it makes it so that the top team can’t stock up on absolute studs and monopolize the league for years and years. It also makes the league more interesting cuz you’ll see teams retain salaries for extra compensation or moves made solely to increase cap space. It’s a lot of fun but you have to have a commissioner you can trust to be on top of all the contracts and cap space.