Apparently pickup at IST airport is still reasonably easy; you may need to communicate via the Bremen phone people.

Note you don't have all that many true FC-offering flights in your itinerary. IIRC CX doesn't offer F to/from BKK. And you probably know that D books into first class on AA flights in the USA (except transcon 3-classes.) Since the price difference between an AONE3 ex-IST and a DONE3 ex-IST is around US$2000, you'll need to decide if the few international FC flights are worth the difference.