Just off the top of my head, at least two Brewers-drafted hitters have made recent all-star games with other teams: Mitch Haninger (SEA via AZ), Garrett Cooper (MIA); Trent Grisham (SDP) likely deserved to go as well.
As to the main question, I think the system is really weak for making big deadline deals, particularly if some key names are off limits. Chourio should be in that category IMO, but it seems like they also have near-term big league plans/needs for both Turang and Frelick. Maybe they move one of Mitchell or Wiemer if they can get a bat with some control (not a rental)?
Small is off limits for some, but I have to wonder how much the Brewers think of him if they gave so many starts to Chi Chi and Alexander. I wouldn't be surprised to see him dealt.
We've recently dealt from medium tier IF and pitching surpluses, but that depth is already depleted and some of the guys they might have used have been hurt and/or ineffective: Zamora, Black, Bullock, Floyd. The pitching someone else might want is mostly far from MLB, guys like Jarvis, Kelly, Carlos F Rodriguez. Maybe Knarr and Shook will get some looks, particularly if the Brewers' rep of spotting pitching talent carries some weight. Cam Devanney and Felix Valerio are IF who might have some value and though I'd be a bit sad to lose Valerio, you could argue that we have a number of 2b types.
This might be the year Lutz is dealt; his numbers are on the upswing (heh) but he seems to have been passed by and will soon need to be added to the 40 man roster.
And that's actually a pretty important note; a bunch of second and third tier prospects will be Rule 5 eligible this offseason if not added....there are way too many to protect, so they are prime candidates for deals. Not all of these guys would stick on a major league roster, but the teams selling often have deep needs for talent and can afford the 40-man slots. Some names on that list (from the excellent post below) that might have some value include
RHP Bettinger, File, Lazar, Jarvis, Vasssallotti, Castaneda, Puello, Cam Robinson, (Abner Uribe injured)
LHP Kelly
IF Devanney, Valerio, Holt, Garcia (!?)
OF Lutz, Joe Gray JR, (Bello, Ward injured)
Kelly and Valerio are most likely to be protected I think. Garcia being on here and so far from the bigs makes him maybe a stronger candidate than I would have thought for a trade, though I think the team thinks pretty highly of him.