I would just go all in as an Omnath voltron build. If you drop the other beaters and a few of the less useful ramp pieces (
Boundless Realms), you would have room for more protection and evasion. It might slow you down by having only one big threat in some instances, but it should help with consistency by making Omnath much harder to remove.
I would also definitely include
Yeva, Nature's Herald and
Vedalken Orrery if you can, so that you can always recast Omnath at instant speed to save your mana pool.