If they absolutely had to remake it, make it the ultimate love letter to fans. Call up Toriyama-san, get him directing artists to make the updated 3D character models, allow players to switch between old and new OSTs, if they're not going to do a complete open world 3D overhaul then allow players to toggle between old and new graphics if it's more of a remaster than a remake, update the motorcycle race so that Johnny doesn't psychically know where you are at all times to bounce you 1000 times, fix some of the endgame stuff with the Black Omen so that it's not just a repetitive dungeon you do 4x, but has more impact on the world.
Dunno, couple of ideas off the top of my head. OG Chrono Trigger still plays so well, the sprites are perfect, the OST is s-tier, and if it's not the best it's easily in the top 3 best 16-bit RPGs.