to be honest, filament absorbing moisture just isn't that much of an issue for me.
so no, drying cabinet is not something I would buy.

I can tell you that spools are NOT standardised.
outer diameters vary quite a lot as does thickness of the reel as does the hole in the centre. I have spools with centre holes from 9mm diameter on up to about 40mm.
I also have small reels that hold 250gms or 500 gms.

Then there's the space such a cabinet would take up. I literally have nowhere to put such a thing.

It's a fairly simple project - but honestly, I doubt you'd sell many.