Have you noticed, though, that every other GP ability does not *directly* impinge on other civs? Instantly acquiring a tech or a building isn't necessarily taking something directly away from another Civilization. I'm all for the GA's abilities to match those of the other GP's, so why not give it the ability to instantly gain a Social Policy? That directly fits the logic you describe.
Another point is that *yes* the other civ can generate great artists & use the culture bomb back-but then what we've got is just another form of unit-based combat (albeit cultural combat). I'd much rather see a multi-faceted (diplomacy, buildings, warfare, social policies) approach to gaining pre-owned tiles (& cities), especially given that such an approach would add to the *flavor* of the game (& to my mind the flavor/immersion of the game has been of increasing importance since Civ3). My feeling still remains that there is no good logic to underpin the decision to remove mechanisms like Cultural assimilation, tile ownership, Cultural "mixing" & Multi-ethnic cities/National Identity when they could have actually been made fantastic parts of the game instead (trust me, I've seen what modders can do in Civ4-& if they can do it, then I'm sure the designers of the game can do it too!)
p.s.: I'm sorry if I've seemed tetchy lately-maybe it was Cabin Fever. I was stuck indoors for 2 whole days due to storms. All the same, I do get annoyed with arguments that amount to "in Firaxis we trust" or "oh, well you just want an expansion, not a sequel" or-worst of all-"just mod it in"! All the same, though, I'll try not to let my annoyance levels get out of control from here on!
Aussie.