At the trade deadline, some teams are "buyers" and some teams are "sellers". The buyers bolster their current team by acquiring veterans for prospects and the sellers trade their veterans for prospects. There are a number of consequences for baseball strategy. Baseball is unique in that the best teams regularly get significantly better about halfway through the year, and the worst teams often get significantly worse. In other sports when you give up a young, talented player for a more productive veteran he is already a member of your team, and likely a contributor in some way (unless he is a future draft pick). Pretty much only in baseball can a team get better without realizing any short-term costs.
GMs like Doug Melvin should consider another type of trade, however. With more teams than ever still sticking around the fringes of competition due to the new Wild Card rules, it's going to be harder to find worthwhile additions from the few teams in straight-up sell mode. Further, the bidding for those scarce players will be higher because any .500ish team thinks they might be capable of making a run.
Like any teams, the Brewers have areas of depth and areas that lack depth. Instead of sending a reasonable prospect for a reserve position player from a "seller", the Brewers would be smart to investigate trading with other contenders (or teams who think they are still contenders) who are looking for middle to back-end relief pitching. There's already a logjam in play, and it's about to get a whole lot more jammed when Jim Henderson and Tyler Thornburg eventually come back.
Beyond the bullpen locks of K-Rod, Will Smith, and Zach Duke (!), the rest of the bullpen is relatively interchangeable, and a few guys out there could net an interesting position player to shore up the depth. There are also intriguing options at AAA that are nowhere near being promoted to the major league roster but could slot into a contending team's pen, such as Mike Fiers or Jeremy Jeffress. They key is finding a team that needs help in relief but has an expendable position player-- potentially someone like the ideal lefty corner outfielder or first baseman with some power. The type of player that could be expected in return would vary significantly by who was made available. Someone like the third Brewer lefty on the depth chart in the bullpen, Tom Gorzelanny, could be very attractive to a fringe contender, and even someone like Kintzler or Wooten could fetch a bench player in return. Then there are more interesting candidates like Fiers (and Estrada) who could be marketed as starters.
The second angle to this is that Jimmy Nelson is quickly forcing the Brewers to make a roster decision. He has utterly dominated at AAA and the Brewers can't pretend they haven't thought about calling him up anymore. Barring an injury, however, there is no room in the bullpen to stash Marco Estrada for starting pitching depth if they are fully committed to the Wei-Chung Experiment. Dangling other excess relievers could be a way to clear up space for Estrada to take a spot in the pen and be available in case an injury knocked out another Brewer starter later.
The Brewers are in a position to make a playoff run but lack the farm system depth to make a huge splash. Turning one of their excess relievers into a bench bat is a clever way to avoid having to bid highly for the assets of the selling teams while improving the Major League team and keeping hold of young prospects for the future. It's an opportunity to get better in the position player department without really hurting the pitching staff all that much, and it doesn't preclude a bigger move to get a late inning reliever, either.