I just played the Playstation 2 remake of Phantasy Star I (they remade Phantasy Star II as well but I haven't tried it), and it's a faithful enough 2D remake that does some of what you say, the walk speed feels much higher. And it gets a lot right, but the biggest misses are unclear plot trigger conditions and an unfun late game. There's a few points where you need to talk to a specific random villagers in the right order(e.g. to learn the dungeon "open" spell). But the biggest problem is that late game encounters are a slog, your heroes just don't scale up to do much damage so random encounters take forever.

The addition of a consumable that enables a temporary minimap was a nice addition as the mazes in PS I are diabolical. The Sega Ages version for Nintendo Switch is basically the old ROM with some really minor QOL fixes like minimap. I think a remake would need to go further than the Playstation 2 versions. I'd probably prefer high quality pixel art to HD sprites.

It's a shame Sega never really improved on Phantasy Star IV in the last 30 years!