I've been a huge fan of Brawn, Glory, and Wonder. They're all great bonuses to give Rafiq.
Reya is one of those must answer cards if you get her into play. I'm trying her out right now. I haven't drawn her yet, but the potential for shenanigans seems awesome.
Garruk is in there because +3/+3 and Trample on Rafiq is actually +6/+6, and is enough to make a two hit kill on a player, along with the elephant cannon and land untapping modes being useful as well.
I specifically redesigned the deck to abuse Reveillark. A lot of the random effects that you want to include (artifact/enchantment removal, targeted countermagic, etc) I just put onto bodies and played those instead of the normal spells.
Cold-Eyed Selkie will probably find its way back in, but normally what I find myself doing with this deck is swinging with Rafiq and nothing else. The Selkie's an awesome source of card advantage, but I haven't found it particularly necessary.
I really like the Masticores because it's reusable creature removal on top of being a discard outlet. They're pretty efficient creatures on top of that. If I didn't need discard outlets so much then I'd be much more inclined to drop them.
I've actually been considering an aura package with Sovereigns. It does work well with my "take eleventy billion general damage" plan, and Sovereigns is a great creature for my strategy in general, so I'll likely end up doing it. The thing I don't like about the enchantments (the Shadowmoor ones anyway) is I don't have a way to recur them. Fool's Demise seems awesome in my build though...
Shapeshifter's a great creature on his own, and it can be Larked back. The Brine Elemental's just an added way to keep people locked down so I can one-shot someone who's trying to race with me. It's another late game "oh wow, guess I win" card, like Reya.
Rhox is another way to gain life with an efficient beater, and well, I have a foil.
Teferi and Tradewind Rider could probably both go in here if I could find slots. Honestly, the hardest part about building this sucker was making cuts and additions. I only got Twilight Shepherd in here and I definitely wanted to get all the persisters in for the colors. I need to run another land or two as well but I just couldn't bring myself to cut more cards.
On sweepers - I've definitely thought about playing them myself. I personally don't normally play more than a creature or two at a time, and considering the amount of general recursion I have, I'm a lot less concerned about it than most decks would be. I should probably have Wrath, Austere Command, and a few other utility ones in here. Thinking about it, that isn't a half bad idea. I'll have to think about it a bit more.