I'd say remaster it rather than remake it, i.e. Shadow of the Colossus, Demon's Souls, Halo Anniversary. New graphics basically bolted on to the same game.
- Leave the content of the game basically unchanged
- Put high-res pixel art or just 2D animated line art in place of the original graphics.
Here's where I probably make it tricky though, optionally I'd also
- Implement modern types i.e. Fairy and movesets/abilities retroactively without changing the teams of trainers of available Pokemon. Like Whimsicott is a Fairy but don't mess with the game beyond that.
- Maybe add a post game to the existing post game, and the post-post game just makes new pokemon, moves, and battle items available in a little hub for online battling etc.
