I don't think you guys remember the weapon damage imbalance that Bard had in ARR. It had to be rebalanced because it was too good compared to every other class. In the case of Scouting versus Healing gear Scouting would give Dancer more HP to work with, meaning they'd be able to boost their healing potency even further than the other two healers by skipping VIT melds, which matters a ton for world first. They also wouldn't have access to Piety outside of melding, but would get access to Direct Hit, a damage stat that neither of the two other healers would be able to replicate. It's not a good idea. They have to be in Mind gear because of those reasons. No exceptions.

Polearms are a weapon that the Ivalice Dancers have been able to use in the past. Given Ivalice has appeared in this game and the speculation about going to Rabanastre in the next expansion, it is possible as a weapon type. It's also Blunt Damage which if Dancer were to be melee dps oriented, whether as a healer or DPS class, would introduce another piercing situation with Monk. So that's a reason it might not happen.