If I may I'd like to humbly suggest that the solution to linking gear progression with the champion system may be staring us in the face. This is an Elder Scrolls game after all

Please mostly disregard the numbers represented. It's the idea I'm trying to convey. The numbers can be adjusted to whatever makes the most sense.
Instead of trying to describe this in words I applied my mediocre photoshop skills to a few images:

There are CP passives that govern each type of armour and weapon categories which are (almost) a 1:1 match with the character's skill tree

Each piece of armor and weapon in the game should change to have it's requirement map to the relevant character skill. This makes total sense from character progression point of view too. I have a higher heavy armor skill therefor I can equip better heavy armor.

I also thought about an additional skill line passive for each armor type called "veteran" with 4 levels:
For example Heavy Armor Veteran would read
- Allows the wearer to equip a single piece of Light or Medium Armor at the current Heavy Armor Level (unlocks at 51)
- Allows the wearer to equip 2 pieces of Light or Medium Armour at the current Heavy Armor Level (unlocks at ?)
- Allows a Single Light or Medium Armor piece to count as Heavy Armor for equipment bonus passives (unlocks at ?)
- Allows 2 Light or Medium Armor pieces to count as Heavy Armor for equipment bonus passives (unlocks at ?)
I like the idea that you have to "buy in" to the higher equipment. Making it a choice feel very "Elder Scrolls" when I think about it. It also helps keep the lower level sets more relevant, especially those I've upgraded to legendary, and by extension the content from which those items drop. It also means that I can respec CP and dump points into the relevant CP passive if I want to use the newer higher level gear early and then build up the other CP passives over time, or I can wait until I've unlocked the next level.
What do you guys think?
(PS: I think something like this could work for jewelry too. Perhaps attached to other CP passives...)