Could be a good idea, but I wouldn't like it to work on AoRA. Too easy. You could also just ask the player if he prefers cutting the blue or the red wire, giving him 50% chances to disarm the nuke, and 50% to get a nice death :p
I usually hate random factors, but this one sounds fun to me (and is not necessary in normal circumstances)
Oh, also WHY can't we fuse a nuke in a level already containing an armed one ? It sometimes could be cool, to clear a level (UC / valuts ? :p), when you got some invulnerability, but armed nuke prevents it... and you rarely have the X needed minutes of invulnerability to wait for this stupid existing nuke to explode.
Any reason to disallow this ?