This technically should be an easy win for Pikkon. If I recall he was much stronger than Cell after Gohan SSJ2 killed Cell for good and sent him to the underworld as was shown when he put Cell in jail. This Cell should have been even stronger than the one that fought Gohan given his Sayain genes but this is unproven. However it still stands that Pikkon was stronger than him. Old Gohan SSJ2 was reputed to have been a lot weaker than he was when he fought Super Cell so given the current evidence and this being a fair fight and all I would have to say Pikkon would win.