In a bit I can go ahead and port over my Sha'ir build from BG. I believe it was the one with Skypledged into Incantatrix.
Sha'ir 5/War Weaver 5/Skypledged 7/Incantatrix 3
There it is. CL 19, full buffing from the Sor/Wiz, Cleric, and Druid list on the Tapestry, plus Metamagic Effect.
In Depth : The Sha'ir natively casts arcane and divine spells, and further already has access to the entire Sor/Wiz list. Being able to draw on that alone makes War Weaver a great option to augment playing GOD with BFC. Furthermore, Skypledged adds in the Cleric and Druid lists, and opens up the ability to get MASSIVE efficiency out of the limited Spellpool slots you may draw upon. And of course, Incantatrix costs you nothing, as you do not lose spells you already know, and your spells known list is the entire list. Furthermore, any of the good ones can be emulated or covered by Cleric/Druid spells even if you do get a DM who won't let you have Evocation from the Sor/Wiz list, so even then, you've lost nothing. And in return, you gain another free metamagic feat, Metaconcert for Wizards, and Metamagic Effect. Now imagine applying Persistent Draconic Polymorph to the entire party via the tapestry.