It might work but then it would more of a pet tank then an actual ranged tank, which would work like how SMN would control Titan to tank for them and sometimes was used in ARR with a team full of dps and one healer with Titan as the Tank. Ranged tanking in general wouldn't work since mobs like to run at you and attack at melee range, which would defeat the purpose of a ranged tank. A ranged OT could work and provide heavy support but it being in the MT roll or dungeon tank could be problematic.