If would you like to add a banner crafting to somebody, you wouldn't .
If I use /recipe give (Name) minecraft:banner command, client is say
Successfully given (Name) the recipe for Air
I know that it's not easy, but I hope you can do it for 1.12. If you can't do it, I hope you would add only the base 16 banners.
Sorry for my English
Linked issues
Comments 3

All NBT related crafting recipes don't use this system.

hi could not agree more 🙂 Firework rockets are now in the recipe book as of snapshot 20w45a. see message send by @unknown added a comment - 05/Nov/20 12:28 AM https://bugs.mojang.com/browse/MC-115229?focusedCommentId=834614&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-834614
Fireworks are WAI per MC-115229