Have just finished my final Gunther novel (Berlin Noir). In terms of Bernie's chronological life I've pretty much read them in reverse order as I was introduced to the books when a friend lent me Field Gray.
I sometimes find myself speculating on Bernie's final days. I see him back in Berlin, living modestly on limited means. The cigarettes, booze and conditions he's endured preclude a long life, perhaps he just about makes it to 1970. Despite his liberal leanings he was still born in the Victorian era and I doubt he has any love for the concrete buildings going up around him. The counter culture? Part of him should celebrate it's arrival but I'm not sure sure he would. I'm afraid I see his well worn cynicism developing into bitterness.
A melancholy view of the end of his life, apologies if this runs counter to anything stated in the novels, it's been a while since I read Field Gray
Somewhere between a spy story and a crime thriller? Bernie can bounce off some of the big players of the time and place like Mustafa Kemal and Lawrence of Arabia. He can go looking for an old German archaeologist / geologist who's got the sole copy of a report about oil prospects in the Turkish Empire; or, spirit away an Egyptian who has proof of the Sykes / Picot Agreement. Bernie's nemesis here could be some nasty British intelligence types - they'd be perfect substitutes for the Nazi's.
Istanbul and Jerusalem could stand in for Berlin. You could even have the stories as a "game of two halves" like some of the existing Germany / Latin America novels except that this time we'd have Bernie as a journalist or salesman in the early sixties rocking up in the Middle East to see what a mess the Brits made of things.
We shall see, but I suspect that would be about it for him as he is significantly ageing by then.
I think Eichmann was hinted at towards the end of GBG, and could have been the next book. Bernie probably would have been fired from Munich RE for getting Max Merten arrested, would have to move again. Maybe he reconnects with his daughter in the USA at some point or maybe he passes quietly, a pauper, from a cardiac arrest, also hinted at in GBG.
I am sure there will be a woman involved. One last act of chivalry, however futile. Dying--to make a difference, redemption.