I have already done it, no big challenge.

It was simple, 4 red chocobo.

And for ppl saying chocobo suck, your totally wrong.

With their movement and choco meteor, they are all dead before they can catch me.
And for the all monster challenge, think about it, you level one, make egg and get infinite number of monster of that level. O.o

Talking about challenge, I have a better one.
Take all battle with 3 characters, no monster, no special character.
To add to the fun, make new strange combo.
3 guy from the start till the end. Im curently doing that, im in chapter 3.
Kinda stopped but i know ill finish it with that setting someday.
Some battle was really hard, like when your group is separated, and you have 2 of your team again 6 enemies.