i had a idea for example in events like the birtday drop party or the Christmas box we get items like a chicken egg with a custom name I Tink it would be fairy cool if they where more 1 of a kind because if u rename items the text will go a little bit on a angle and i Tink it adds a nbt tag or a rename tag to the item it would be cool if those items dint come with rename rags or other changes that u would normally get by renaming a item in a anvil so they can only be made by staff and given out at events this can be fairy cool
promos already exists that are renamable. While they are few and far between and usually 1/1 items they do exists. The most recent one to be released I believe was the manuscript and that was made final. If you want a renamable promo your best bet is to probably buy one.
I get what you mean, but I would reckon that enough promos are given out as is. You're right that the renamed items do not have (much) extra monetary value, but it can be fun to get them.