I'm going with the Archer idea - I'm playing one, a complete killing machine. I just want a better longbow
If you're playing a good-neutral party, a single-class thief, cleric or mage would be a good idea - as there are no good singleclass mage/thief/clerics that you can keep for the whole game. Or maybe a tank (Cavalier, Berserker) - with good stats, those get pretty powerful.