Out of all the Draco Meteor users, Mega-Rayquaza has the highest SpA stat, but considering it needs Dragon Ascent (a physical move) to mega-evolve, it would need to be a mixed set, which is certainly viable, but might be less than optimal.
Behind that, White Kyurem has the second best SpA stat (of DM users), and considering its SpA is also its highest stat, special sweeper sets are quite common for it.
However, I also feel inclined to mention Kingdra, with its 100% crit set. In case you don't know, after a Focus Energy and a crit-enhancing held item, Kingdra has a 100% crit chance, and crits bypass the user's stat drops, so Kingra can just start spamming Draco Meteor with no regard for the SpA drop, especially if it managed to get an Agility in as well.