If we are to keep magic and elements the way they work in FFXIV, a Ver-Blizzard/Umbral Ice would be the go-to way of regaining mana.
Of course it does not have to be a proper stance mecanic as BLM, but it could be an oGCD that turns into VerBlizzard if your Black mana is higher, delivers an ice aspected magic attack with a MP refresh, or VerWater if White mana is higher (her I'm not sure what it could do because Water magic in White Mage is almost non existent). Make them AoE to soothe the crowd wanting more AoE on RDM