I think you could add more spells that make eldrazi Scions.
Catacomb sifter could be useful here for setting up the pieces. Creature based mana ramp is very easily disrupted. I either recommend land finding spells, Artifact/Enchantment mana ramp, or Call of the Scions type effects. All of which would play better than
shaman of Forgotten Ways and
Beastcaller Savant.
Hedron Archive isn't as good in this case as
From Beyond, which can be used to ramp into 6 mana or beyond, or sacrificed to find a missing combo eldrazi. Still loving the synergy of
Siege Rhino and
Eldrazi Displacer. Instead of just attacking for 4 every turn, it also forces your opponent to lose 3 life too. Not to mention the ridiculous amount of incidental life gain you will get from blinking a
Siege Rhino once or twice a turn. The only down side I see to
Eldrazi Displacer, is that it is the biggest combo maker I've seen in awhile, which means it is also the biggest target at all times when it is on the battlefield.