How many volumes are there supposed to be? 3? If so, one could swap out the US discs if they wanted.
Though I think someone with a little more expertise in exchanging the inside casings could take out the 1-disc trays, put in two disc trays (or three with a lone one on the right if wanted - or a sticker hub) and only get vol. 1 and vol. 2 and use it for both series (with the '1' and '2' on the spines representing the seasons).