Something I think FFXIV does that is somewhat appealing to me is the concept of these little miniature raid 'zones' with a bit trash and then a single boss at the end each with a unique theme (fire zone with Ifrit, ice zone with Shiva, for fans of FF series). These raids are 8 person, but the mechanics are tuned ruthlessly hard where a misstep can wipe the whole party and long, complicated multi-phase fights. These raids come in addition to the main 'tiers' of raiding and act as catch-up or supplements to gearing up.
So taking this back into WoW, would you be interested if 6.2 contained a 8-12 (flexible scaling within that range, locked to 10 person in Mythic mode) person 'raid zone' with say, some void elementals and then a multi-phase Ner'zhul fight, to beta-test? We haven't had a raid with the intimacy of Kara since... ever, in my opinion, so I think it'd be fun to have a raid that fits between 5-mans and 'real raids'.