Well, actually there is a Professor in Darmstadt (one of the three partner universities in the GSEFM, the structured programme in Frankfurt) who speciliases in Economic History, his name is Caspari. His class also gets a fair bit of guest lecturer from good universities (Friedman from Harvard in 2015, and James from Princeton this year).
As for development and applied micro, there are professors working on this both in Frankfurt and Mainz (the third partner university in the GSEFM).
The placement record, to be honest, varies enormously. Some (few) students place extremely well, as their webdiste likes to boast, but the vast majority places average, or even goes to the private sector (not that I am denigrating the private sector, but just to say not everyone goes to the IMF or Harvard).
It is definitely not common place in Frankfurt to go for the MSQ and then apply for a different PhD and since I have never heard of anyone doing it, I can't tell you how professors will react. Although I am fairly sure Professor Binder (the head and founder of the GSEFM) will not be happy and probably should not be your go-to for an LOR later on. I think Barcelona's master is more accustomed to that, but as you say it is only 1 year, meaning you kinda have a year in between where you re not in the programme, but you re not in a PhD either.
Since Frankfurt's master will probably never have been heard of in North America, you ll probably need to get a 1.0 to 1.3 for it (thats the top 2 possible grades in Germany), which is very difficult, although achievable if you work very very hard at it.
On the plus side, if you re not interested in the PhD in Frankfurt, then you dont have to care about prelims, and need only focus on the midterms and finals for each semester. Which means you would actually have holidays in August/September, unlike the rest of your cohort
Again, however, I dont know how professors will react to someone wanting just the Master and wishing to pursue a PhD elsewhere, since this is most definitely not the norm.