The deck's a fun one to pilot, the modularity leads to games shaking out quite differently. One game you feel almost like Naya goodstuff, the one after you quickly copy a narrow beatstick. There's still some clunkiness hiding in the execution, but there's not a ton that can be done about it. Maybe reorient the deck a bit towards the Rhino plan, cutting down on the number of sliding pieces and situational includes? But what's the fun in that? 
MH2/AFR wise, far and away the most viable include is Serra's Emissary. I'd have slammed it in in a heartbeat if it hadn't turned out unfun in testing. My build makes some concessions in the interest of table-wide fun, as ultimately this is a social format and winning with this deck doesn't seem worth it if it comes at the cost of deeply disgruntled opposition. Of the cards EonAon brings up, Flame Blitz could be a meta piece of walker hate if there's a lot of those flying around. Tireless Provisioner is not the worst thing in the world, but it rewards a lands.dec playstyle the build isn't aiming for. You can technically bank some of the mana you make, unlike the original Lotus Cobra, and it interacts favourably with token doubling. However, if Moraug failed to gel, I can't imagine Provisioner being too successful either.
In terms of AFR, the most viable card is Wulfgar of Icewind Dale. Given the fact a worrying proportion of the deck's beef is attack trigger based, this not only amplifies Ghired but also Kalonian Hydra or Boomgoat. However, the problem is the cost - five mana conflicts with Ghired and most follow-ups. Nevertheless, I gave it a couple of test games, and the results were about as expected. In the first game, I lacked action, so Wulfgar combined with Parallel Lives to churn out four Rhinos a combat until I drew into Boomgoat. Spoiler, Wulfgar's double melee translates to a very juicy stat line to spread around. In the second game, I had an Ohran Frostfang and other 5+ costs, and Wulfgar sat in hand as other stuff got played out instead. So yeah, he's ultimately kind of like Cat Car - a bonus synergy piece to make use of things that already came together. The deck is still keen on minimising "what-if" layers, given its modularity. I could see this being ran in a more Rhino focused build.
Other stuff worth mentioning:
- Delina, Wild Mage would be a consideration for some mid tier copying if the token didn't come with the exile clause baked in. That's a bummer, I thought we left this templating behind after Shards of Alara? Thankfully, Phantom Steed in the same set has conventional wording. Delina's an outlier, formulated the way she is so the two rolling outcomes can build off each other more clearly. Phew, hopefully no more Heat Shimmers in our future.
- Druid of Purification is a decent option to try to get some multi-target removal going. It does technically depend on the table cooperating, but it shouldn't be too hard to get a little discord going between the other three players. The main issue is the cost - spending four for removal is a bit more than the deck likes to. In fact, the three-drop answers are already often a bit clunky.
- Guardian of Faith is the second mass phase, and automatically becomes the second best three drop juke spell after Teferi's Protection. Thing is, we're already not running TefProt for clunkiness/curving-out reasons.
- Teleportation Circle has the magical cost of four, and is actually a consideration for Rhino builds or just ones that go heavy on ETB value.
- Vengeful Ancestor is a cute option for trying to keep your foes' prime beef away from cracking back into you. My group has a bizarre hatred of goad, so I won't be able to test how this does. It's probably too silly and tangential to what the deck actually wants to be doing, but is nevertheless an option to consider.
