Oh, hey, didn't see this thread!
To chime in on the whole Avatar debate, I like Robin as an avatar because he makes sense as the player character. Robin's role in the game is to be the tactician Chrom found in a ditch and brought onto the team because, well, Chrom is decidedly NOT a tactician. If "Hit it with Falchion!" doesn't work, he's out of ideas. So Robin gets to order people around and generally does a fine job of it, though he does defer to Chrom, but Chrom is perfectly happy to let Robin handle this. And what's the player's role? To be a tactician and order units around! Perfect overlap of player role and avatar role.
I'd like to see another Robin, the brains behind the Lord, so to speak. Let the Lord do the royal things and let the player avatar handle the tactics. Corrin being both the Avatar and the Lord just muddled that up. When Corrin did something you as a player didn't want to, it broke the connection. Cleaning up Chrom's messes was fine. Creating messes yourself because the plot said so... gets annoying. And it doesn't help that Corrin's personality doesn't really fit the tactician mold, yet she is still leading everyone, even those that outrank her. To use that phrase, Corrin as a ludonarrative dissonance problem. The character presented does not seem capable of performing the feats you as a player must do. Or make the choices you as a player would have made, despite being an avatar character.
So if there's another avatar, please let that person be a tactician or otherwise tactical minded person. It makes the connection between player and avatar that much stronger.