The reason for senate-involvement is to provide a normalizing force — consider the reason that most conservatives wouldn't vote for Ron Paul as president "he's got terrible foreign-policy" [or 'military-policy' or similar]. Well, that's the reason for Senate involvement: so that those other positions are filled with people that are acceptable to the President as well as the States themselves [via Senators], that way you can have a guy who's brilliant with some stuff [but not with others] be President.
These appointments are supposed to serve the whole of “We, the People”...not the platform of a political party.