Agree with the others: definitely no veto, especially in a keeper league.
Each manager has to be able to improve his own team now, so they should be able to address position and category weaknesses even if a trade is imbalanced (not lopsided). Corpas was a 7th-8th round type of guy, Rios a 4th-5th round type of guy. Close enough with Hudson thrown in there.
And managers also need to be able to judge for themselves the future the value of a deal - this is where this being a keeper league is key. If one manager thinks that Rios is injury prone, or likely to get dealt to a pitcher's ballpark, or whatever - he might have his own reasons to devalue a guy more than others would.
"The government cannot give to anyone anything that it does not first take from someone else"