Just as the title says, ik the whole motto is that its a simple backpack but you only have 3 backpack models to make and it would probably satisfy a large amount of people seeing the only backpack mod for fabric that supports trinket is garbage (Traveler's backpack).
Again it would be an optional thing for people that want it, so yeah its just if you have time for the models.

I do not really like Trinkets and the messy slots all around the player in the inventory screen. I see no need to add more complexity to the mod with trinket slots and 3D models.

If you are looking for backpack mod with Trinkets support, perhaps you should check out Inmis

https://www.curseforge.com/minecraft/mc-mods/inmis

And another author made an add-on to improve Inmis model: https://www.curseforge.com/minecraft/mc-mods/inmisaddon

Please keep in mind that the entire purpose of me creating this mod was to have one that had minimal external dependencies (like Trinkets, GeckLib, etc) that could be updated and used in most current fabric and snapshot releases. I do not wish to stray from that original goal. Frankly, I remain shocked that it has received as many downloads as it has with the availability of much better backpack mods.