Opum is not only unnecessary as a character, he's downright offensive, as if one can't be both brave and intellectual.
This is where you lose me. I think you are wrong for two reasons:
1. As Captain Miller clearly shows, one CAN be both brave and an intellectual at the same time. He was obviously college educated, like Upham, and was also a school teacher. If that doesn't scream "intellectual" then I don't know what else does.
2. Upham is an essential character in the film as he is the one who helps flesh out the character of John H. Miller. They both identify with each other as they are both intellectuals and they seem to form some kind of bond that isn't present with the other men in the squad.
Upham was a non-combatant, having not held a rifle since basic training. The only reason he was pulled into the mission is because the translators Miller had in his company had been killed. Because he wasn't one of them, and because the guy had not seen a lick of action, the veteran guys in the squad were destined to pick on him.
Despite his weak and cowardly nature, Upham becomes the moral compass of Miller's unit on their quest to find Ryan. In fact…I would argue Upham is most instrumental in making the key part of the story happen. After Wade is killed in their assault on the German machine gun position everyone, including Miller, wanted to execute the German POW on the spot. Upham was able to change Miller's mind and the German soldier is set free. As we all know, this same German soldier goes on to be the one who fires the fatal shot that kills Captain John H. Miller.
My favorite scene of the movie is the one where Upham, having listened to Mellish getting killed from the confines of the stairwell, stares up at the offending German. Upham has a clear shot at this guy. The German has no rifle, just his bayonet, and is completely and utterly defenseless. Upham, however, breaks down into tears as he finds himself unable to take the man's life and allows the German soldier to pass him on the stairwell to continue the fight against his comrades in arms.