Yes, it's a hardware problem. As I remember, there is a single select line for each DFx:. You'd have to separate the select line for DF0: out of the cable and bring it out to the select pin for DF1:
External drives used to wire the "next drive" select line on the incoming cable to the "DF0" select line on the output connector. So you could have up to three external floppies, chained together. I once tried it with three external drives (and the original internal), but the A1000 power supply couldn't carry the load of four drives at once :-D
tony