Also includes dead weight like Grossman, Hoes, Wojo, Chapman, and Peacock, although of course even if you don't plan on keeping those guys you do need at least some of those spots for MLB-ready players to fill in when needed.
I would say Jandel Gustave is a near-lock to be added as well, considering he was taken last year (but returned) and had a very nice year at Corpus, lowering his walks substantially. He could conceivably help in Houston in 2016.
Aplin will be an interesting decision. No power whatsoever but I think he could be a very useful 4th OF, with a slight chance at everyday CF/leadoff man. He had a .413 OBP this year between Corpus and Fresno, and walks more than he strikes out. He bats left but can hit lefties, doesn't hit into DPs, has outstanding instincts/routes in the OF, and can steal a bag. He certainly seems capable of helping in Houston next season, so no real harm in adding him to the 40-man in place of Grossman or Hoes, if you believe in him.
Maybe guys like Paulino and Teoscar Hernandez are being dangled as trade bait right now. Even Fontana I'd hate to lose, although he's been a disappointment. Devenski is another one that would suck to lose, but it's hard to find room for all these guys unless Luhnow's got a trade or two up his sleeve to clear some space.