One may have torpedoed the other. It's like putting two rival racers into one of those old student driver vehicles with two functioning steering wheels.
Ridley with anybody, I just don't know. But the man knows exactly what he's doing when it comes to making movies. If he can just be kept away from the script, wonders could be worked all on his own.
As or Neill, keep him away, far...far away. I don't want to see Aliens go the way of Robocop 3.