I think my good buddy Vorel of the Hull Clade would work nicely in this deck...especially in conjunction with your favorite card Fathom Mage. Nothing quite like doubling up your counters and drawing cards, haha

I keep trying to get a Simic deck to work myself as I love this color combo and I love drawing cards, but for some reason I've had very limited success. I wish you the best with your version though! +1 from me!

I had Vorel in a very early version of this deck. He was too slow, though, and I needed more sources of counters. He's great with Fathom Mage but I'd really rather use him as the general of a different deck.

This list works pretty well. I attacked someone for 50 or so with an Overbeing of Myth the other day, and that kind of thing really isn't uncommon. You can go more combo-heavy with more Maro-style cards and Conjurer's Closet or you can do more of the ramp-stompy with Zegana to refill your hand. This list can do both.

zegana can also be combo-centric with deadeye + lab maniac, or many other combos in the colors (Mind Over Matter + Temple Bell + eldrazi in deck is a personal favorite for its difficulty to stop).

I would strongly consider Garruk, Caller of Beasts in this build. He's powerful.

I actually just took Garruk out. He kept putting my counterspells and sol rings on the bottom of my deck. I put in Garruk, Primal Hunter instead. I do certainly use the Deadeye Navigator + Laboratory Maniac + Prime Speaker Zegana combo, but I don't beeline it.