Keep in mind I haven't played Mana in years, so I may be completely off at some points.
Well, how would you feel about an updated remake? And not just in graphics. It's storywriting was one of the best for the 16-bit era (though I thought SD3 was better), but it still has 16-bit era story limitations.
Take the villains, for instance. What were their motivations besides conquering the world? Did you know they got their powers (even Vandole) from Underworld deals with devils? I sure don't remember that little tidbit when I played way back when... yet it was apparently present in the Japanese release. And what exactly
was Thanatos, BTW?
Add to the fact that Thanatos was able to bring so much tragedy because Purim's father didn't want her to get with a commoner. The fact that this is never really truly addressed or that they guy was not called out for it is mind-boggling.
Maybe flesh out the world as a whole as well. As for gameplay, I'd want to keep it more or less the same, but with one noticable change. More party members and a character switching mechanic. Jema and Luka must be playable, dammit!
(Seriously, was I the only guy who voted for Watts?
)