After reading through another "why is turning useless" post, I figured I'd throw this idea out there.
One of the famous ways a cleric could use turn attempts in a non-core-only campaign was by taking the Divine Metamagic feat. The most popular way to use it is coupling it with the Persistent Spell metamagic feat, which makes the spell last 24 hours.
My suggestion is to give Divine Metamagic (Persist) to all clerics for free. Allow a cleric to expend Spell Level + 6 turns to persist a chosen spell until the next rest. I would expect the majority of players to use it for things like Prayer, which wouldn't really be imbalancing. Bards already grant much better bonuses essentially "all day" since the songs cannot be dispelled. These persisted spells would be subject to dispels as normal, however.
What do you guys think? I can't think of any buffs in DDO that would imbalance things if this were possible.
At least it'd give clerics another option for turn attempts besides DV's and Divine Might.