Originally posted by Eric Evans:
Why wouldn't it invisibly add itself to the lead ace packet? Thereby leaving three indifferent cards behind.
Your concerns are easily addressed by asking yourself a simple question: "What EFFECT do I want to get across?"
In routines like "MacDonald Aces", the effect is, essentially, TRANSPOSITION. The aces TRANSPOSE with indifferent cards in the leader packet.
If that's what you're after, then starting off with a leader packet of three indifferent cards and an ace makes sense. But the question remains. WHY are you transposing the aces?
Sometimes, your presentation justifies the transposition. For example, in the context of a gambling routine, there's no reason to question why a poker dealer would want to switch his indifferent cards with the aces in his opponent's hands. Wesley James' "L.S.D. Aces", and Simon Aronson's "O'Aronson's Aces" are prime examples of this approach.
On the other hand, if you want the effect to be a VANISH AND REPRODUCTION of the aces (a somewhat related, yet thematically different effect), the most logical thing is to do away with the indifferent cards in the leader packet. Moreover, after each ace vanishes, only three cards should be seen in each respective packet. David Copperfield's routine is a good example of this. In his version, no other cards are in the leader position other than the leader ace. This makes sense. It's unnecessary for any other cards to be there in the beginning, since the aces will eventually be reproduced there.
"Collin's Aces" is another case in point. Not only do the aces vanish and leave behind only three cards, but it also gives you the freedom to reproduce those aces anywhere you want. If you vanish all four aces, they can be reproduced say, in your wallet, or spelled to, or under a drink, or anywhere your whim and sense of mischief dictates.
Dustin raised an interesting question. Why even have packets at all? What if you just put four aces face up on the table, wave your hands over them like chink-a-chink, and have the cards assemble that way?
Or how about the best of both worlds - a tabled reverse version of Travelers. You put four signed aces face up on the table. Vanish three of the aces, one by one (or put them into your pockets), and then reproduce them by moving the fourth ace aside to reveal three aces underneath it.