For example, first, I make Script A.
Then, I make Script B.
Then, I make Script X, which chooses a random percentage, and then, it says, if the random percentage is 49 or less, then cause Script A to be performed, but if it is 50 or greater, perform Script B.
I think this is at least theoretically possible. After all, it is possible to put leveled items INSIDE leveled items. For example, if I want an NPC to carry a random, leveled sword, but that sword is randomly either a shortsword or a longsword, then all I have to do is create a leveled longsword (between iron and daedric) and a leveled shortsword, and then create a third "leveled" item that has both of those other leveled items, but they are both available at level one. That way, whenever the item is chosen, it could be a steel shortsword, or a steel longsword.
So, because you can have leveled items within leveled items, I'm pretty sure that it's possible to have scripts within scripts. But... how do you do it?