Mythic + / Fractals
This is an idea I'm copying from Guild Wars 2's Fractal content.
In GW2 there are Fractals which is basically Mythic +. However GW2 Fractals have 4 Tiers 10 levels each.
The higher the Tier you climb the more Fractal Resistance you need to negate the negative debuffs. I think Mythic + should feature the same mechanics.
Right now if you want to be competent in high level Mythic + you need Heroic Gear from raids. This is fine, but for me personally I don't enjoy raiding. I think it would be better to give Mythic + Resistance to Mythic Gear for those who gear thru Mythics and upgrade those gears with Mythic Coins.
People who raid can still do high level Mythics w/ their Heroic gear, while those who only do Mythic + have a clear direction to work towards. We can select our gears from Mythic 0, then upgrade them as we climb the Mythic + Tiers.