This is quite a niche suggestion but I believe it could add a interesting new layer of customization and RP for our characters.
It’d be nice if we had the ability to transmogrify or catalyse our existing bags into different bags of our choice. For example the Sunfire Silk Backpack does not quite match the aesthetic of my characters (neither the icon or the ‘Sunfire Silk’ name and material). This idea would still involve existing content as it would require obtaining a bag with the desired number of slots like a Sunfire Silk Backpack for 38-slots.
If I could acquire both a Sunfire Silk Backpack and an Imbued Silkweave Bag then transmogrify or catalyse them into a 38-slot Imbued Silkweave Bag, it would look and feel more appropriate for my Nightborne characters.
I could imagine my Death Knight with 38-slot Deathweave Bags, my Earthen Shaman with 38-slot Earthen Satchels, my Warlock with Felcloth Bags, Draenei characters with 38-slot Draenic Leather Packs etc. Unique bags, such as Elementium Toolbox could be a suitable alternative for the reagent bags that are available.
This would also create a small market for bags from previous expansions.
As I reread what I put above, I recognize just how niche this idea would be but it’d be nice to have this additional layer of customization for what I see on my screen.