Is it possible to have a ranged attack of opportunity?

Question

I have a player that is looking to create a house rule for the Beast Protector feat that would allow him to use his basic ranged attack rather than his basic melée attack. This works thematically from the perspective of the ranger as a ranged combat expert (Robin Hood archetype), but I worry about play balance. All of which leads to the question: is there a build/feat/power that would allow a player to substitute their ranged basic attack in place of their basic melée attack for attacks of opportunity?

Answer 1

Sharpshooter - Ranger's paragon path from Martial Power (p.67) has this:

Opportunity Fire (11th level): You can use a bow or a loaded crossbow to make opportunity attacks. These attacks don’t provoke opportunity attacks.

Answer 2

There are Paragon feats that do similar

Opportunistic Archer

Paragon Tier Prerequisite: 11th level, elf, fighter, Combat Challenge class feature Benefit: When you can make a melee basic attack against a target because of Combat Challenge, you can instead make a ranged basic attack with a bow against the target. The ranged basic attack does not provoke opportunity attacks.

Published in Martial Power, page(s) 144.

Answer 3

You should also consider Spitting-Cobra Stance, also from Martial Power (p.47):

Ranger Attack 5

Effect: Until the stance ends, you can make a ranged basic attack as an immediate reaction against any enemy within 5 squares of you that moves closer to you

(this wording is from the November 17, 2009 rules update)