There *are* other Str-based cleric powers that you can use with a fullblade or mordenkrad.
The powers that don't *require* a simple weapon are those that give +1d6 damage if you use a simple weapon. If you have access to a d12 brutal 2 weapon superior weapon, you can use that instead of a 1d8 + 1d6 simple weapon.
Take inferior role-fulfilling powers that confer no benefit at all and waste a turn if I miss, just so I can use my mordenkrad...or take a power that actually does provide good role-fulfillment with a little extra oomph if I hit, but, for no logical in-character reason at all, says I have to wield a simple weapon to use it. Yeah, really tough call.
I did in fact say that the powers that deal extra damage with a simple weapon are fine. It's all the simple weapon only stuff that upsets me, because it's
patently better than everything else a Battle Templar can get, and yet for some reason they've felt the need to tell me I can only use it with an ordinary club. Even though there's an entire game mechanic (weapon proficiency) already established that they could use instead to try and favor the simple weapons, with expansion for personal choice/flavor requiring the use of feats (which is what the feat space is intended for).
If you want to give simple weapons a unique edge, do it through advantages, not exclusivity. And for pete's sake, make it fit the flavor design, not just "because I said so" or "because charop will break it if I don't". Because that's all I'm getting from these powers right now.
Edit @
frogged : My point stands all the stronger then. If the base cleric can only use simple weapons, then this restriction is completely unnecessary. Weapon proficiencies cost feats, which is a fair investment for that sort of flavor customization. Don't automatically cut those out of the picture by restricting your weapon options on top of it.