It would have visuals similar to Tales of Vesperia.
For character designer I would pick the artist that did Childen of Mana. Not too many non human characters like LoM did. I guess a fat cat is a must have for the series now.
I would make the overworld similar to Ni no Kuni http://www.youtube.com/watch?v=nlPlq7-0Bs4&t=3m50s
. Flammie is a must.
The ring-menu must be back. The gameplay continues as the ring-menu is open. This way coop gameplay is possible and fun. Same thing for magic: The game doesn't freeze as magics are displayed.
Magics with different effects; are useful.
Dungeons should have small puzzles.
A standard RPG. No SD4 stuff.
For story, something simple, but with twists here and there.
I would do visible weapons AND armors.
Can equip and use 2 weapons @ once.
Skill tree similar to LoM, where you get more skill as you go.
A more action rpg style core gameplay. With block button, not just stats evasion etc.
As for music; bring back Hiroki Kikuta.
I would name is SD5: Secret of Mana 2
This game makes itself.