Best practice for entity with hierarchy (like a catalogue)


I would like to create a hierarchical catalogue of items. My first throught is to introduce a new entity and start from the ElggGroup code.  The entity should have relationships, support hierarchical categories and have similar behaviour/features as Groups.

The result should be a catalogue of cars with drill-down from Brand (Volvo) > Sort (Stationwagon) > Type (V70) > Serie (from 2005-2008). And the members of the site are owners of the car.

I'm new to Elgg and would appreciate some feedback on the idea of a new entity derived from ElggGroup. Any thoughts an suggestions are welcome.

Thanks in advance.