RePEc could also accept multiple formats. But that means that they need to be converted anyway for the metadata to be used. One should note that RePEc is pretty much defined by the format it uses, as that is the only thing that binds this informal organization. Finally, the philosophy of RePEc has always been that the cost of data entry is borne by the publishers, who are those that benefit most from RePEc. We have no in house resources that can help them beyond what volunteers contribute. So ultimately, it is all a question of finding volunteers to do what you want.