The most obvious step would be removing the politically protected deadwood in the Army of the Potomac's command structure. Butler et al thwarted Grant's plan to envelop Lee. Grant's strength was always to take what actually was happening in the battle space & keep fighting. As Sherman said, Grant really didn't care what Lee or Butler for that matter did. He was going to keep pounding away no matter what either one of them did.
An interesting thing that could have been accomplished was the destruction of the Augusta Arsenal. By 1864-65, the majority of Lee's powder was coming from Augusta. A raid could have left no stone standing. There was absolutely no way for the CSA to replace the supply of superb quality powder from Augusta. It is possible that Lee would have run out of ammunition. In any case, I am happy it did not happen. If the Yankees had blown up the arsenal, the explosion would have flattened my wife's family home & who knows if we would have ever met.
As a mature student of the Civil War, to me it is more than passing strange that anybody takes D.S. Freeman's depiction of the losers as the best generals & best fighting men. The tactical victories without strategic impact of the A of NV are glorified. The Overland Campaign that beat Lee like a drum until he holed up at Petersburg & awaited defeat is held up as one long string of A of NV victories. Perhaps it is because I study the Western Theater where victory is defined by surrounding & accepting the surrender of your opponent that I find the that I find the D.S. Freeman version an artifact of a age rather than an objective history.