I really enjoy a good fan theory, especially when there isn't an "official" theory published by the creators. However, I've been dissatisfied with so many of the ones out there (for Shadow of the Colossus) so, I decided to write my own. You can find it here .
It contains everything from when Wander holds his sword to, sound effects to, dialogue choice to, changes in the weather. Big elements such as the purpose of the Colossi and, whether or not Dormin was actually the one who resurrected Mono, are all explained in-detail and without contradiction. It is even consistent with Fumito Ueda's personall views on the story.
Come check it out and I hope you enjoy!