Walking Ballista can fit into a lot of different strategies, and your ability to mess around with it and mod it like a weapon in a game, makes it a truly outstanding card, and definitely one of the best Artifact Creatures in Commander
Growing Rites of Itlimoc is about as close as Magic has ever come to printing a functional reprint of a Reserved List card
Both effects work with each other, and in fact, you will most likely need to play Present Arms first before the creature's baseline effect can do anything
Seemingly designed to be an MTG Commander, he's in the spell-slinging Izzet colours, and as you read the card, you'll certainly be envisioning a Storm-y spellslinging deck that looks to combo off - as each time you cast an instant or sorcery you access a different ability That is, until you reach the final line of the card and get a rude awakening
This is the point where the nonactive player might cast a flash creature to ambush the opponent, after attackers have been declared