While indexes and constraints are global, they likely effect the exported subgraph too, so to recreate a subgraph in another DB fully, indexes and constraint should be exported too. 
In order to achieve that, a DB reference must be passed to the CypherResultSubGraph class, so that index and constraint definitions can be accessed. Furthermore, the ExecutionResult should be checked for used labels and for every used label *the index and all constraints of that label* should be added to the export. Sound about right?