What if there were no difficulty Tiers and Blizz just took a page from M+ and let Raids scale? We’re getting Raid versions of Affixes in Season 4 so maybe it’s on their radar.
I’d say smaller Raids (5 or less Bosses) that scale like M+ with scaling rewards. Lose all difficulties for Raiding and 5 mans other than keeping LFD/LFR since there’s a market for queued content.