Halo 5 needs to have a lot more armor customization options than Halo 4. Halo: Reach offered a lot more armor customization options than Halo 4 which made it a lot more awesome. Having a lot of armor pieces to unlock makes the game even more fun by giving you an extra purpose for doing certain things or completing certain challenges.
How to unlock/get armor:
Ranking up your SR-rank
This will simply unlock basic armor pieces, nothing special or unique. This will unlock a good amount of armor and one a special armorset if you reach the highest SR-rank. This will add lots of customization abbilities for players to customize their spartan but it will not include any ‘Legendary’ armor pieces except when you reach max SR-rank, than you will get a Legendary armorset.
Ranking up your CSR-level
Everytime you rank up a Division you will unlock a Legendary armor piece. When you reach the highest Division rank you will have a full Legendary armorset. Each playlist will have it’s own CSR level (this has been confirmed) and with each playlist you will be able to unlock different Legendary armorsets. This will motivate people to play different playlists and will create a lot of goals for people to achieve (unlocking special armor is always exciting).
Ranking up your CSR-level in temporary special playlists
It would be cool if 343 would add special temporary playlists that offer a different ruleset and will also include special Legendary armor that will only be available in this temporary playlist meaning your armor will be rare and unique. I would suggest these playlists to stay for a week. When the week is over, the playlist will go and your chance to get the special Legendary armor will be gone as well.
Completing multiplayer challenges
You will also be able to unlock new armor pieces by completing challenges. For example, if you get 50 assissinations you will unlock special arm pieces. Ofcourse this would also include special Legendary armor pieces for completing monthly challenges (which would take a lot more work and dedication to complete them).
Completing Campaign missions and campaign challenges
If you complete the Campaign you will unlock a new armorset, if you complete the Campaign on Legendary you will unlock a Legendary Armor set (Master Chiefs armor). Adding monthly Campaign challenges will motivate people to play the Campaign again. Campaign challenges could include completing a mission on a certain difficulty, completing a mission using a specific weapon or killing a certain amount of enemies in the campaign with a specific weapon. This would add more replayability to the Campaign and would also add some cool armor pieces to the Multiplayer.
EDIT:
Completing certain achievements, finding all skulls and that kind of challenges should also unlock armor pieces/armor sets.
Please let me know what you guys think about this! I think this would be really awesome!