I ... tend to choose who gets which weapons based on how they fit the character stance-wise, and general feel-wise haha!

I once resolved to give Master Thief Vaan only daggers and ninja swords but gave in and gave him swords (but only certain ones with names that seem to fit the "hero", like the Ice Brand, the Demonsbane and the Deathbringer) so he looks like a hunter. I actually think Balthier looks fine with a bow (took a little getting used to) , sort of like an elf (and because guns are slow, though the Fomalhaut is very tempting ) , and gave Basch the katanas, also to increase his speed. I think Ashe looks good wielding a spear, so does Fran but I gave the latter handbombs and when I get good blades / slinky swords, there. I give Penelo daggers and ninja swords. For back-up, I give think Basch and Ashe are fine with guns, Penelo has a crossbow and Vaan looks like he has a bone to pick with the monsters with his handbombs.