4-Color Scapeshift with Bring to Light and Nahiri the Harbinger.
Nahiri's primary function is not pulling a creature to the battlefield, but controlling the board state and dealing with combo-breaking cards such as Leyline of Sanctity and Blood Moon. Her +2 helps fix the hand and being able to pull a Primeval Titan with haste means +4 lands to the battlefield. I've found Emrakul the Aeons Torn to be not very effective in this build; while it is possible to make Emrakul happen, top-decking Emrakul is the absolute worst. Sure, Nahiri can filter it back into the deck, but for the most part it's a dead card until then and that hurts too much to make it worth it. I do put Emrakul in place of Primeval Titan when Mill shows up at my local meta.
Nissa, Steward of Elements: Scry on a stick, strong possibility of cheating out an extra land or a Sakura-Tribe Elder, and an alternate win condition- it's basically a Hunting Wilds with more value for less mana. It isn't so much of a threat that it demands an answer from your opponents, but it can draw their creature-fire which is always a plus. The only way this XGU planeswalker could be better is if its +0 ability just said "Search your library for a land and put it into the battlefield," and that's probably asking too much. The only downside to Nissa is that we can't get much value out of its potential 3-mana CMC since we don't have access to out turn-1 land ramp on the second turn. That means the soonest we can cast it is turn-3; but this planeswalker is insane in a control matchup.
Prismatic Omen is primarily for the games where you're suffering from Mountain-flooding early in the game as it makes basic Islands etc. enter as Mountains. This also means that Valakut, The Molten Pinnacle can trigger itself upon ETB, which means casting Scapeshift on 6 lands can result in 12 Valakut triggers for 36 total damage. It's important to note that similar to how Khalni Heart Expedition is too clunky to make turn-4 Scapeshift the prime directive, getting a turn-4 Prismatic Omen/Scapeshift shouldn't really be the main goal. I've found that having 3-4 Prismatic Omens too frequently resulted in drawing a second one around turns 3-5, when I would have wanted actual land ramp or a board-wipe. This was an issue especially when Prismatic Omen was in the opening hand. This also makes Worldly Counsel go from searching the top 4 to the top 5, making it significantly better than Anticipate and less restrictive than Peer Through Depths.
Delay instead of Remand because access to Bring to Light means 2-4 extra copies of Scapeshift, making cantripping less necessary. Delay also keeps your opponent from immediately recasting the spell, and entirely ruins counterspells as they won't have targets when they're ultimately cast. Theoretically, if your opponents' spells are coming off suspend, they're either too late to make a difference and the game is yours, or your own topdecks were so bad that you were never going to be in a position to win.
Izzet Charm is the flex-spot in the deck. Worldly Counsel loots better, Delay counters better, Supreme Verdict is way more effective in a meta filled with Death Shadow. An argument could be made for Lightning Bolts or Sudden Shock instead, but Path to Exile does not go in this deck. One-drop removal isn't as necessary because of the critical mass of lands we have in play by turn 4 (turn 3 on the nut) and giving your opponent a basic land in exchange for removing their creature essentially gives away the land-advantage you are trying to secure early game. I'd even use Declaration in Stone over PtE.
