It'd be awesome if the Zelda team could take a brief break from Zelda and do a Golden Sun remake with Camelot (though I guess Monolith Soft did help with Breath of the Wild's world design). :D
I think, spiritually, Golden Sun's atmosphere/tone is more closer aligned to Zelda than most other RPGs out there. For example, I would not be a happy camper if Golden Sun came back and the script now had swearing/cuss lines added to the dialogue. I like my heroes, or at least the MC/player character, completely clean of any strong or even mild language. A Golden Sun remake needs to keep some of the humor as well. Both these aspects might come down more to localization though.
I think Golden Sun is about exploration, maze navigating, puzzle solving, and a deep battle system with strategic potential. Just as equally, I do think the characters and story/world building/lore is part of the Golden Sun experience as well, even though I'd like the dialogue to be trimmed a good deal for better pacing with the game-play, I wouldn't mind various ways and side quests/optional skits to further learn about the world and characters without slowing the main story down too much. Plus we need skippable scenes so we can get straight to a boss fight if we lose the first go around, amongst other QoL additions.
As for artstyle, I don't care as much, as long as it looks good and true to the Golden Sun official artworks. It could go for Lord of the Rings realism, or Avatar: The Last Airbender toon style. Either way, I'll be happy as long as characters keep their basic established look (Isaac with blond spikey hair and blue eyes, scarf, etc. Jenna, red head, same attire as original games, no drastic clothing/armor changes for anybody. Gotta be recognizable from their currently established/iconic appearances.
And for music, would love a live performed remixes of course. Otherwise, I dunno. I feel like the GBA sound chip gave Sakuraba's tunes a more unique flair than his usual output. And's there's Isaac's battle theme, the first half of which sounds like nothing I recall ever hearing from Sakuraba before, which further helps make Golden Sun a stand-out amongst Sakuraba's various works over the years. If he came back for a remake, I hope he can reattain an emotional score with modern synths/samples and/or live instruments. Great music is also core to the Golden Sun experience.