Well, if you're keeping the names, I'd have done the other way around then: use Lucia as main elf, and have Tel'Erond as secondary, with different abilities, since he was a mysterious character in the original game. But that's just me.
I guess Lucia sprites are good for other classes, but it wouldn't be Lucia anymore though - she's instantly recognizable as the Elf, and "elf" in basic D&D meant fighter/wizard multiclass.
That said, you can make it work.
I like the idea of a "darker" hero (as unlockable character), but it feels weird seeing Lucia sprites fill that role when she was the sweetest cutie pie of the bunch, so if that class is necessary, I'd choose another base (though esn23's edit proves she can be a hell of a necromancer!).
Bard is a support class that could bring a lot of fun to a 4 player game (not so much when you play alone), with "buff" spells and songs that affect the whole group, and still feel generally different than the other spellcasters. Even her fighting style matches a bard, with elegant moves. I'm not bothered by the lack of "instruments" in her sprites, you can add those in the animation, just like bows magically appear in the character's hands in game
Like BeasTie said, her original sprites work best for a druid. You'd have to add a lot of summoning spells, weather magic, and specially, the ability to shapeshift into an animal, turning her into a dual class: spellcaster when elf, melee when animal. Different animals, different abilities: wolf is fast, bear is tough, eagle flies, spider is poisonous, etc.
Anyway, don't feel like you HAVE to bring Lucia into the game, if she wasn't on your plans. Even if you add her exactly like the original Elf (maybe as a bonus unlockable hero), that would already be a nice gift for us. ^_^