Besides wanting the developers/publishers/whomever to cough up cash for Iwadare to write music for an Orchestra again...
I would not object to another coming-of-age story like the first Grandia. Personally, I would have it where there are two love interestes to chose from, with the option of choosing one of them half way down the road. After choosing, the other choice separates from the group--taking with them one or two of the other party members with them--and the hero is left to their choice and perhaps other party member(s).
Along the way of the journey, perhaps the hero begins to feel second thoughts on their decision, as well as feeling betrayed/uneasy on the speedy departure of not only the other choice, but the party members that accompanied the other love interest as well. Perhaps the hero made the wrong the decision? Every now and then, the player will have the opportunity to shape the hero's thoughts whether they made the right decision or not through choices in dialogue.
About 3/4th into the game, the hero would have the opportunity to bail on their love interest of choice, leaving them and the other party members that stayed with the group/joined along the way. This path, the Indecisive path, would have the player traverse alone for a short bit, until introducing a new love interest character, as well other new/returning party members along the way. This third love interest would act as a replacement for the other two.
From there on, the ending of the game is determined by whichever love interest the player chose, as well how confident the hero made the right decision when picking that love interest.
Of course, the point in all of this is that there were no wrong decisions on any of the choices, only the indecisiveness--or Steadfast Conviction--of the player.
Hrm...this actually deviates from anything Grandia-like. Never mind! I'm keeping this for my own game. :P
Oh, and I would keep Grandia 1's battle system and graphics (by that, I mean an upgraded/better quality cartoon-like images).