So the above Istanbul workout addresses your concern. We can produce a 200gp GM/GA in Istanbul. Either way we can save a GA for our third GAge.
We do not want to do that.
Saving that GArt for the 2nd golden age is great, but we would not want to save it for the 3rd GAge. If we do that, we run the risk of getting 2 artists

Berlin and Athens will make our 100% guaranteed 3rd Golden age along with a GS.