Vanilla used to have item degradation back when the quality was 3 digits. This is a feature I seriously miss. There are just no item stakes anymore. Now once you get a high quality item, you never need to craft another one or work on the skills to craft one. (Hint - Put your points into lucky looter Level 5 - Not the ability to craft better things)
I miss the days when I used to have to decide "Hrm is damage to my level 540 pickaxe worth it just to bust down that door since I'm a long way from crafting 500 quality items? Is there a window I can go through?"
I also miss the days when the items durability bar was down 50% the item did less damage...
I'd be just fine with keeping the mod slots.. once you have 4 slots, always have 4 slots. but as the quality decreases so does the base damage that the mods multiply.
I made a mod for my server to randomize the modslots anyway. You might find a level 1 pickaxe with 6 slots, or a level 6 pickaxe with 1 slot or anything in between. more combos , more variety.