the real realignment would be separating the major markets from the small markets into different leagues so there'd be some real competition on the field. the small markets are just basically glorified minor league teams for the major markets at this point since they cannot financially retain their top players and have to trade them around the time when they can start making real money in arbitration or free agency. That's coming from a Brewer fan in a season when they have the best record in baseball too at the moment.
I get what you're saying, but MLB actually has pretty good parity. In the AL, the worst team is a very large market (Chicago), and the only other team winning fewer than 45% of their games is the As. The NL is a bit worse, but even there the Brewers are dominating, as you say.
But, what MLB needs is either a hard cap, or a really punishing NBA-style luxury tax. Only a handful of teams need it -- the Dodgers, Yankees, Mets, etc. -- but it would be good for the league. Particularly fan interest: no fan likes seeing all of the major free agents select from maybe five rich clubs.