one thing i’ve always wished for in halo games was to create your own emblem 
You can to a extent. MCC gives you options but you’re limited.
Custom emblems are great and all but people do abuse that system with offensive content as seen many times over the teams in games like CoD - they’ve since removed that custom emblem system due to that issue.
The game would then have to have a content filtering system. Which would maybe work to a extent but there’s always work arounds that people find.
I think generally it’s easier to just have the current system or something similar.