I think those items are really useless and that only new people can actually enjoy such add-on, but the majority will just ignore the addition

If the items added are stronger than vanilla, enchanted netherite/diamond swords, we risk unbalancing PvP. On the other hand, if the items added are weaker, then they simply will not be used IMO.

all of these metals have a purpous and none of them are diamond, and even for the enchanted iron, non of them provide more protection / damage than diamond
heres an example
this will not unbalance pvp, also i can help you in changing any of these values, because i know programming
Copper sword= iron sword Smite 2
copper Armor = leather armor Blast protection 2
Tin sword = iron sword Sharpness 1
Tin armor = iron armor Blast protection 3
Silver Sword = iron sword sharpness 2
Silver armor = iron armor protection 2
aluminum sword = iron sword bane of athropods 3
aluminum armor = iron armor  blast protection 2
lead sword = iron sword sharpness 3
lead armor =  iron armor protection 3
zinc sword =  iron sword sharp 2
zinc armor = iron armor protection 3
Magnesium sword =iron sword sharpness 2
Magnesium armor = iron armorprotection 2
steel sword = iron sword sharp 5
steel armor = iron armor protection 3
damascus steel sword=  iron sword  sharp 7
bronze sword
so much more, but the max damage and protection is cobalt, with iron sword sharpness 7
and iron armor protection 7
and reinforced being sharp 8 iron sword


also ALL OF THE PREVIOUS ITEMS HAVE VARIABLE UNBREAKING VALUES RANGING FROM 1 TILL THE MAX BEING 10

Also important thing, ALL OF THESE VALUES ARE EDITABLE, AND SINCE I MY SELF CAN PROGRAM I CAN EDIT ALL THE VALUES FOR YOU TO SUIT YOUR SATISFACTION, I GET THAT YOU MAY NOT TRUST ME.