Multani seems decent if you want to ramp into the 7 slot, and can act as a finisher with the right deck (probably the Sultai version, as they may put more stuff in to the graveyard). The fact it has built in recursion and anti-flying is nice.
I'm not necessarily sure how much we should push beyond the 5 slot in general, though. I like having Carnage Tyrant as a 6 drop at least in the sideboard (maybe mainboard depending on the meta), as it's a massive headache for some bad matchups (looking at you Control). Biogenic Ooze is ultra awesome, and it even pumps up Vannifar to a 3/5 the turn it lands, and can easily end games. Lyra is crazy good for the Bant version.
The thing I most enjoy about this deck, though, is you really can adjust / pick what you feel best fits your local meta / arena / Bo1 or Bo3. It doesn't take much adjustment (assuming you own the land, of course), to change between R/W/B, as there is potentially loads of overlap, or some of the creatures you might want are 1 ofs anyway.
What I'd love to see if anyone starts bringing a version of this into tournaments.. and if we start getting match writeups in standard.
i'd love to see an Pro list too. The problem i see for now, is how Sultai is on the edge in this std. With many removals (chupa, Throphy, Cast down...) and Vaniffar need to untap to start to work. I start to think to use Dive Down to protect it. And this is the reason i like to use other must answer card like Thief of Sanity and Biogenic Ooze (full playset in mb). Toolbox is my favorite archetype.
Still playing sultai version, made another 3-1 last showdown (last monday here) i'll put whole list before, if lands and i need to improve my side.