I really, really don't see him that way. He is one of the most generous politicians I've ever seen in terms of spending his political capital for the benefit of other Republicans (sort of like his friend President George W. Bush), he worked like a dog on other Republican campaigns, some successful and some not, and he is VERY community-oriented without blowing his own horn. He has a tremendous amount of personal energy and he's not afraid to use it for political or community good.
That said, it would be wise for President Bush to consider appointing either Conrad or Dorgan to the Ag position, for tactical reasons as well as the fact that they both portray themselves as conservatives (at least during election years) on agricultural and economy issues. It would be "bipartisan" and it would get them out of their life-tenure seats (as it seems) in the Senate. Then Hoeven could appoint Schafer or any one of the other very strong conservatives in the state in the interim.