As it looks like now Clerics has 3 things that put them a part from FvS:
the option to swich spells
more spells
the ablity to turn/destoy undead
It would be reasonble to let at least of the 3 comming Cleric PrE have one of it's focus on turning (for example combined with healing). Asuming that Warpriest will be the prestige class for the battle Cleric (eg melee oriented Cleric with low charisma).
Apart from the obviouse heavy increase Clerical turn Level that are needed for turning to destroy undead in a magnitued compared to the cost of high charisma (100% or 200% more for some math look at: http://forums.ddo.com/showthread.php?t=167986). I sugest that you follow the pattern that you use for Bards farsinate.
Make more creatures turnable obviouse choice are:
*) fire, ice, earth and air elementals (as the D&D 3.5 domains)
*) the abilty to exorcise an extraplanar creature as the Silver Flame Exorcism .
To make it real fun it could work like this:
PrE lvl 6: you can fire, ice, earth and air elementals and you Clerical turn Level increase with xx
PrE lvl 12: you can use turn attempt to exorcise an single extraplanar creature (same mecanism like "destroy" in turn undead OR using the Silver Flame Exorcism mecanism) and you Clerical turn Level increase with zz.
PrE lvl 18: you can use turn attempt to exorcise mutiple extraplanar creature (same mecanism like "destroy" in turn undead OR using the Silver Flame Exorcism mecanism) and you Clerical turn Level increase with yy.