As far as I'm concerned, a high power gestalt should have as many of the following:
1) Full casting for at least one tier 1 class.
2) Breaking the Action economy (got stuff in my sig about that).
3) Several of: Full BAB, 6+ skills, D10 hit dice, Fort + Will saves
4) Class Features
I'm looking for a mostly casting-centered build (we already have solid melee), but I'll be taking the Transformation domain so that I can handle melee when the party splits up. In other words, melee features aren't a big deal, but I don't want to be helpless in close quarters, either. Perhaps Warshaper?
I'm surprised you suggest archivist/wizard-- it's a lot of spells, but you still only cast one or two per round, right?
Mostly casting-centered but still silly in melee? DMM persist is still top notch.
Cleric 5/Church Inquisitor 10///Beguiler 15 for double casting and skills
Cleric 5/Church Inquisitor 10///Tome of Battle Material for heavy melee
Cleric 5/Church Inquisitor 10///Factotum8/Tome of Battle to grab extra standard actions + Swift leap + White Raven tactics to be silly
Cleric 5/Church Inquisitor 10///Wizard 15 (which is obviously a mistake) for insane casting. Only 1 or 2 per round? Nah; Celerity, an item to provide White Raven Tactics, some belts of battle, quicken spell? 3-4 per round.
I still think Church Inquisitor is a mistake past 2, though. Cleric chasis is passable, and church inquisitor is weaker than divine orcale, RSoP, Dweomener Keeper, contemplative 6, all of which would be lovely for a casting cleric, and whatever is on your offhand side will probably benefit more from a prestige class than cleric is.