In the lore, the differences are a lot like the real world, honestly. The fact that Rangers in Final Fantasy have generally used Bows, that's not the identity of the job by any means at all. The notion that there's a necessary link is a fallacy brought on by previous experience. However, Rangers have also been known to wield:
- Boomerangs (Final Fantasy II, XI)
- Daggers (Final Fantasy V, XI, A2)
- Bouncyballs (Final Fantasy X)
- Crossbows (Final Fantasy XI)
- Guns (Final Fantasy XI)
The abilities, however, have the common theme of nature. This is because a Ranger isn't necessarily a "User of ranged attacks" as much as it is "Ranges over the terrain and is a master of everything on it." Think less FFXI ranger (though it did have Widescan...) and think more mountain ranger. Or Aragorn. Or any other use of Ranger outside of Final Fantasy.
Many do fight from a distance and have abilities like Aim, but the nature theme extends to tracking animals, calling on their abilities, etc. Also, Rangers are more reliant on doing DAMAGE via ranged attacks where as ARCHERS are more reliant on tactical damage dealing, as in attacks that, while they do a bit of damage, more importantly do things like control enmity, inflict status effects, bind the enemy, etc.
Ironically enough, one of the Rangers from FFV was dressed in a bard outfit.
Either way, Ranger uses a LOT more than bows, and Archer has always been a status inflicting class. Giving it Bard makes 10x more sense than anybody has given it credit for so far.
Seriously; naysayers on this topic, I invite you to disprove any of this and state a counter-argument more productive than, "I don't want to do any support! I JUST WANT: BANG BANG BANG!"