This suggestion is pretty simple - add banners made on normal crafting table using wool, after placing make it open a paintlike program. Banner's neutral, named after player: "Banner of lv1crook". It auto-sets to player-specfic protection. Also, make banner bearerrs able to use custom banners. I hope this will get implemented.
Suggestion by Herobrian333:
If added a gold/silver ingot in banner crafting recipe in faction-specific crafting, then protection works just like with normal banner, therefore it being customized.
Criticism open