Just played the demo. It is undeniably cute, seriously impressive number of past FF characters too. And everyone that has had a voice in the past has a their same one which is kinda surprising. When you get to the final boss, open the chests around him for little mini trailers showcasing FF characters, Summons, monsters, etc.
It took me about half the demo to figure out this stacking thing, it wasn't making sense to me at first, but I get it now. Each type of monster has a L, M, or H label and that's the only place in a stack they can reside. Your characters can only be on the bottom in their full-size forms, but in their chibi forms they can be in M to ride on L monsters like a Behemoth. You can switch between chibi and full form for each cahracter independently at any time on the map, and you set up your stacks for each character and each form.
Catching monsters is VERY pokemon. Most monsters you just have to weaken before you can "Imprism" them, but others have special requirements. To catch a moogle you have to cast cure on it, others you have to hit a weakness, etc. Each monster has it's own little ability tree that you can unlock nodes on in the menu, each monster earns experience independently.
The battle menu is a bit interesting, you can set up four shortcuts to be mapped to a face button, or you can press L1 to bring up your classic menu with your full list. I didn't realize you could customize the other menu until right near the end of the demo.
Anyway, I can definitely see the customizability options with the monsters...even though the stacks still look awfully goofy. (Certain moves also can throw you off balance and topple your stack, stunning you for a turn, and you can do it against enemy stacks as well.) But I'm fairly sure I'll enjoy this game