Ok so Sundering Titan = banned so cut that, I'd say add something like Illusionist's Bracers.

My biggest thought is why run the soft counterspells? You're going to be tpp busy building your board (or at least you should be) to hold mana open to counter spells. Then by the time you've got free mana open people should be able to pay for your counters. Honestly if you're gonna run em, make em good. Also unless you're a really tempo oriented deck I wouldn't play Remand in EDH.

Check out stuff like:

Arcane Denial

Dream Fracture

Into the Roil

Dissipate

for spells that will help you deal with problem permenants.

I'd also toss in straight-up polymorph as it lets you do things when your commander isn't around.

Also if you're willing to drop money on Consecrated Sphinx why no Blightsteel Colossus? Seems way better for your deck.

Roil Elemental, Prognostic Sphinx. and Pearl Lake Ancient all seem really ineffecient in this deck. They feel like the worst things you can hit and honestly unnecessary. Maybe toss in the common-drazi if you want something cheap to take their place, or It That Betrays and Spawnsire of Ulamog are both non-legendary and pretty solid beaters. Also Platinum Emperion is a beat stick and maybe worth a look.

See Beyond and Dream Cache are cheap ways to get cards out of your hand and into your deck so you can polymorph into them. Scroll Rack if you like expensive cards (I have one fyi which I could trade if you thought you'd use it)

Crystal Ball in place of something since it lets you scry dudes to the bottom and gas to the top.

More mana rocks. This deck will want them prety badly for when a dude does get stranded in your hand.