I got my cases in the mail today. These are the ones I ordered:
https://www.ccisolutions.com/StoreFront/product/mediasafe-audiobook-case-new-6-disc-optionThe look of them is a good fit for retro computer games. The internals will require a little bit of modification but it'll be an order of magnitude easier than modifying UGCs to fit NES games, which many of you are familiar with. A pair of $5 flush cutters will get the job done just fine, and they should be able to fit multiple disks with sleeves, with enough room for scaled down reprinted manuals, copy protection sheets or whatever other print items you might want to put in. I'll look into designing some kind of template for it, maybe one that's the usual "cover-in-a-cover" with wide decorative borders for those taller box arts, and one that's more minimal for things like the old EA LP-style or covers that were square and more appropriately shaped for this kind of case.
I'll make a new thread for it once I have something. I'll start with Commodore 64 since that's the system I have the most 5.25" floppies for right now. After that I can try doing MS DOS, and hopefully get around to Atari 8-bit, and then Apple 2. I don't think the VIC-20 is worth bothering with since afaik there were hardly any games released on 5.25" floppy disk for that system anyway. With an appropriately sized foam cutout you could put 3.5" disks in there too or even CDs (that's what this case was made for after all), but at that point you might be better off with just a UGC or DVD style case to better preserve the artwork. Having options isn't bad though, if you are insistent on having a uniform collection.