Add:

Borborygmos Enraged: Turn lategame lands into advantage

Chaos Imps: Huge Flier

Chromatic Lantern: Best Mana Fixing

Death's Presence: Capitalize on Big Creatures

Explosive Impact: Removal

Giant Growth: Combat Trick

Glaring Spotlight: Lethal Swing

Hellkite Tyrant: Big Flier

Madcap Skills: Powerful Evasion (note, does not make a creature unblockable with Alpha Authority)

Maze Behemoth: Gives Commander Trample

Mizzium Mortars: Board Clear

Molten Primordial: Removes big blockers, gives additional attackers, and can act as removal

Rogue's Passage: Gives creatures unblockable, like your commander that has to keep attacking

Skarrg Goliath: Combat trick that kills defenders and players

Sylvan Primordial: Ramp and Enchantment/artifact/planeswalker/land removal.

Thespian's Stage: With being limited to RTR lands, why not get out of set lands?

Utvara Hellkite: Wins games on its own

Viashino Shanktail: Firststrike Combat trick (also called SHANK tail)

Weapon Surge: Combat trick/mass combat trick, turn trades into chumps

Worldspine Wurm: 15/15 that spawns 5/5's

Wrecking Ogre: Combat Trick Doublestrike

Remove:

Bomber Corps: Doesn't do much, the battalion isn't reliable, and ping isn't useful

Experiment One: your deck doesn't spam creatures with ascending power/toughness.

Foundry Street Denizen: Doesn't do much of anything, wasted slot

Spire Tracer: 1/1 faux flier doesn't help

Skinbrand Goblin: small combat trick, weak creature

Gatecreeper Vine: defender in an aggressive deck that searches out a single card in deck

Skullcrack: a useless card, even for an aggressive deck, burn is used for creature removal

4x Mountain: Too many lands

5x Forest: Ditto

Mending Touch: Regen isn't worth a card

Pyroconvergence: too expensive, Shocking on multi-color doesn't help much

Skylasher: counters a single faerie a turn, doesn't do much else

Tablet of the Guilds: lifegain doesn't matter, wasted slot

Gruul Charm: doesn't do anything

Maybe:

Hellraiser Goblin: Gives all creatures haste

Illusionist's Bracers: 12 damage with Ruric Thar, the Unbowed, instead of 6

Racecourse Fury: gives any creature haste

Seek the Horizon: Ramp

Street Spasm: boardclear

Tower Defense: anti-fliers if you are concerned about that

Zhur-Taa Ancient: ramp for all, also really cheap big guy

Turns out Sylvan Primordial is banned in commander, so scratch that suggestion