Obviously, the very first thing people want is cross core coatings and visors, since those will be easiest, then cross core, but I believe the next step to allow the most unique looking Spartans will be to allow more helmet specific attachments to be used on other helmets.
A lot of these specific helmet locked attachments have the ability to completely change a helmet, or just make the helmet look more unique than just throwing a flashlight on.
I will be editing in examples of helmets with the wrong attachments on, that look good in my opinion.
https://media.discordapp.net/attachments/856815463963164723/973428278251638804/0d30e63b-e5a0-4b8f-af31-673084a40447.png
https://media.discordapp.net/attachments/856815463963164723/972970695548096593/f438a036-a701-4c1f-bfb7-6e6651312044.png
https://media.discordapp.net/attachments/856815463963164723/974072420656885840/a103f744-73ac-4479-aafb-03b952efba19.png
https://media.discordapp.net/attachments/856815463963164723/975109632135684156/bf3abf02-eefc-4d76-9665-7089f1ac8902.png
These may not be perfect but im sure just adding a little here and there will make it looked polished enough