I would stick with Relational Databases and model. As far as I know, Hierarchical Model was not used since nineties. You can emulate Hierarchical model in relational database, but I do not see any advantage in doing so. The setup you described is a very common relational setup and will be easy to implement in FileMaker Pro.
You can try to lookup NOSQL as alternative, probably document-orientated systems are the best match, but the cost is going to be very high in comparison with FileMaker and you probably will not be able to do it yourself.