In the far future maybe Mehmet Scholl if he´s had some first team experience, in the near future Klopp or Tuchel. Definitely not Kahn.
+1000
I doubt Klopp would do it anytime soon though, not necessarily because he said he wouldn't breach his contract at Dortmund for it, but I don't think him to be the type who'd choose to take over the national team if he had the chance to take over another club. I suspect he'll want to stay in the more fast-paced "club business" for as long as possible, not solely at Dortmund of course. Might suit his personality better, too; although he's definitely one of my wish candidates as well. (His comments at the pre-Arsenal conference sounded a bit like he'd be genuinely interested in trying his luck in the Premier League - maybe take over Arsenal from Wenger?). Scholl could indeed be suitable in the future, hadn't thought about it before but makes a lot of sense. Kahn, lol. Hopefully not.
[...]These 3 examples are just a little piece of the puzzle. In my opinion, Sissi reached his tactical climax in 2010 and it's going slowly downhill since then. He gave the team all he has to offer, but now he should leave. It would be better for everyone.
...especially for the general concept he/Klinsi brought about, which, as I said before, I'm
generally hugely in favour of. If he leaves after some great failure, this will take away any legitimation from the style of football he introduced, feeding those who criticised him and the concept and leaving the job open for those who would prefer to go back to the steretypical German efficiency kind of style. In the end an elegant style of playing doesn't weigh much in comparison with trophies, at least in the eyes of some, and a trophy is exactly what would justify the philosophy. But since his potential seems to be exhausted (as you said), it would be much wiser of him to make place for a like-minded person with some fresh ideas and a little more in-depth understanding. This is the only way he can see the fruits of his work and prevent the foundations he built from being torn down for something else. This is what I'd genuinely like to see, too.
As for his tactical understanding, I'm torn between thinking he just lacks a deeper understanding/knowledge of football (to suceed at the micro-level, as you called it) and thinking that he overestimates himself and just likes to try out allegedly undoable things for the sake of it, similar to Pep in his last season at Barca. (By which I mean Pep's eccentricity at times; I'm not seriously comparing Pep with Löw or saying Pep overestimated himself). It might be a mixture of both. Can he improve? I don't know, but what I noticed is he has started to become predictable in the general approach to some issues and his way of making decisions, which makes me pessimistic. In hindsight, Özil as a false 9 this seems 100% Löwian, with his handwriting all over it.
But since he's not leaving for now, I might as well wish him luck and to suceed. I'm tempted to hope Germany will fail greatly to force him out, but due to the things I mentioned earlier this might result in an even worse alternative.