I think there are some serious difficulties in changing how baseball works.....
Other sports can really be dominated by a handful of elite players, and rookies. Not true in baseball at all.
A team needs 40 players to get thru most years. There aren't enough good players to go around. The lack of FA until a player is past his prime makes signing FAs not always a good investment, but if you want a floor, you will force awful teams to sign veterans to real money, and play them instead of youth.
Just changing how money works isn't going to help. It just means the A's sign 1-3 players that suck every few years to good deals, but they still don't win. And they slow down the development of their young players.
You'll have to make FA come sooner (meaning wealthy teams have more good players to add to their team, ironically) to give mid market teams a chance to add actually good players in FA.
The NBA is utterly dominated by a handful of elite teams, because of team size. There are just as many teams out of the playoffs by mid season as there are in baseball. It's marketed better and more interesting to watch to fans.