Peter killing Norman, if he felt the character-appropriate amount of guilt for it afterwards, could actually result in genuine character growth for him - as he struggled for redemption and his conflicted feelings over saving lives by committing an act that he himself nonetheless considers wrong - something that he's been totally devoid of throughout BND. Plus, it would rid the MU of Norman Osborn, which would be The Ultimate Good.
So, yes, Peter killing Norman would be better, in every possible way, than everything else that's happened in both OMD and BND, all of which have been garbage.