Story wise is kinda hard. Maybe mages or Peg Knights?
Flavour wise, I really like Master of Arms (you didn't put it in :[) and Archer. I like the thought of being able to use multiple weapons proficiently, adapting to the situation, and if I got to pick, I would take out Lances on MoA and put in Bows instead.
Gameplay wise, probably mages. I love blasting fools up with magic, and enemies generally have low Res in all FE games, so mages tend to be awesome units.