In the simtihing table in 1.16. You can only upgrade your tools/armour to netherite. I was thinking if you could add new gems such as Rubies, Topaz, Amethyst. Allowing you to upgrade your amour, Each armour set piece you can put a certain amount of gems (Example) Netherite chest piece you can put 2 gems. Each Gem would give you an upgrade and set bonuses may give you better upgrades. Each gem will give you certain upgrades. Topaz would allow you to mine faster if you put a topaz gem in a gem slot in your armour And if all pieces have topaz gems in them you would get a another level of fortune on your pickaxe. Amethyst will upgrade your chance of getting more enchantments and make enchanting cheaper and getting experience faster. the set bonus would be all enchantment prices would be 25% less. Ruby would improve your strength making you stronger and reduce your cool down by a bit the set bonus would be you can have rare chance to one hit mobs (this does not work on bosses) Gems are found at Y level 1 to 16 and are rare as netherite and only spawn in a one block vein. There are 3 gem ore types Rubies, Amethyst, Topaz.
Diamond is a gem itself, and we already have a ton of enchantments. I personally don't like a concept of overlapping enchantments with physical upgrades.
Especially when it requires creating additional minerals - we already have a nice bunch.