I really wish someone would return to making something along the lines of the old Ultima I Matrix, which had interchangeable runners of many types - though their (aluminum?) bolts and nuts (with tiny hex key heads that stripped easily) were a bit problematical. There are people who drill through their boots, so they can quickly bolt blades on and off, especially if they have the same hole positions (e.g., if they are the same model & size, which doesn't apply here). I think that is mostly used by people who skate on synthetic ice, because their blades can't go long between sharpenings, or by people who like to mail their blades back & forth to a preferred skate tech. But It's a common way to mount roller skate chassis.
If I put guards (usually hard guards) on my blades, I can carry both skates in one hand. So I could carry two pairs in two hands. (I don't actually need the guards, but without them, I have to be careful not to cut myself.)
There are also plenty of reasonably strong mesh bags and backpacks available, though I don't know how large your skates are and whether they would fit any particular bag.
If you are flying or taking public transport with your skates, would a bag that conceals the skates could make them a "concealed weapon"? The primary thing that makes a skate bag good is ventilation - so an open or mesh bag seems best. E.g., type
paddling mesh bags
or maybe just
mesh bags
into a search engine. Some of them are full size duffel bags, are relatively strong, and are relatively cheap. Add "wheels" into the search if you need them - but that ups the price.
(If you have done much kayaking, canoeing, or [I guess] sailing, scuba or cold water swimming, you are probably very much aware of how much neoprene spray skirts and wetsuits stink if you don't air them out. And sometimes that gear can be heavy.)
I have sometimes used IKEA mesh bags to carry wet gear. Some are really cheap. Also, mesh shopping bags that are rated for a reasonable amount of weight.
But I admit these mostly aren't as stylish as Zuca and Zuca-like bags. And you can't race on top of them, like some kids like to do on Zucas.
