Load or merge several already generated graphs

I’m trying to achieve an offline routing service, and for that I’ll need to either:

  • load several graphs (related with different OSM files), one after another
  • merge several graphs and load them later (in a mobile device)

As I read in https://github.com/graphhopper/graphhopper/issues/293 merging different graph files is not possible yet, however, what about loading different graph files and sending a request that potentially could have a part of the route in different graphs?

If none of the options above are possible at the moment, could anyone suggest a way of doing it?

Is there any way of generating a graph for an osm file (the planet one, for example), and then cut it in smaller pieces (countries, or regions for the countries with too much information) so we can perform routing from a place in France (with a graph for France) to a place in Switzerland (with a graph for Switzerland)?