Gokou didn't have the energy to completely obliterate every piece of him. That is why I don't think he could win. But fighting as long as he could, wearing down Cell, would have been better. Gohan may not have actually needed to go beyond super saiyan if Gokou had tired out Cell at the least. What I don't get it why Vegeta didn't go the staying super saiyan thing for the year he trained in the Spirit and Time Room when he realized what they did and why they did it.
What has Vegeta ever done that compared to Gokou letting a villain stay to fight his son and forcing his son to fight? Cell he gave a senzu bean and he could have easily ended Buu by killing Fat Buu yet he wanted Goten and Trunks to do it instead. Goten and Trunks wanted to fight Buu sure but that still is no excuse.