The skillset in Celerity is a weird combination as is, though. It's got shades of Ranger through Leg Shot and Aim, but Shadowbind is usually more of a Ninja skill, while Wind Slash originated from Sabin's Blitzes. Quick Hit has been in the Ranger skill set before, but I always mentally associate it with Tidus, who is a swordsman/speedster/time mage. I can't even recall which other games had Quick Hit besides FFX and FFD at this point, though. Did FFV Ranger have Quick Hit? I recall FFV Ranger having Barrage as its major skill.
Anyway, the point is, that Irvine, despite wielding a gun, does not actually get any of these skills, whereas characters like Tidus and Fran actually -have- gotten them in their games.
Now that said, I -totally- think that if Rinoa and Squall get Celerity, that Irvine should too, but uh.... oh well? The word "celerity" literally refers to speed, so it's not -actually- the Ranger skillset. Which explains why other ranged characters like Sazh don't get it either.
FFRK:
Wanted to play with my toys, so I made a team of all-physical 5*-loaded combat characters to see if they could autobattle through some Elite-level content. They Mastered the 90-difficulty Demon Wall in Golbez's event without much trouble, though I did switch to manual to throw some Drain Swords.
All Lv65, all 5* or better gear, all rocking 4* damage abilities + a Break or Spellblade
Cloud w/ 6* Zantetsuken+ rocking Holy Blade materia
Tidus w/ Brotherhood and Double Hit
Squall w/ Blitz Sword and Self-Sacrifice (and Drain Sword)
Lightning w/ Ras Algethi gun and Zealot
Sephiroth w/ Keepsake Knife and Gore-Stained Blade II
It's not as good as Mage Meta, but surprisingly effective when you can actually use all your best gear in one party. (Why can't I get a freakin' 5* mage weapon...!?)