I never liked the AOM pop sistem at all. The max pop there was 300, and even though it was 100 more than in Aok units generaly costed 2 times more so armies were generaly about the same size in both games.
And another thing the else/pike idea is a good example but ppl generaly forget about one big factor. COST+TRAINING TIME!
I am generaly a Michi player, never got close AOM on zone, and i have faced hundreds of eles/pike situation. And now for everyone i would like you to consider this scenario.
"Bla bla bla at min 33 a celt guy cuts they aren't able to enter the game get to 1 hour and by that time there is a Pers on the other side who has managed to gather 100 Elite War Elephants.
Ok now this gets interesting, i never panic under these situations, on the contrary i would like to see something like this more often, so now there is only one thing you can do.
Just keep kill the elephants with what you got, at first it may seam imposible that you send Halbs and lose them in seconds but you must not forget that Halbs can be trained in seconds and you can train them constantly and with good defence you will see (probably to your surprise) that eventualy the Elephants are killed."
And now the Pers is crippled, he just wasted 200000 food and 75000 gold on an army he has lost and he won't have the resources to make another one like that.
Now I am not just making this up, I have faced situations like this and I have won.
And besides I will say this again, I don't think you will get any Elephants in AOE3.