Many thanks to SaltandPepper15 for the detailed review. I won't be continuing the Burning Earth Storyline. It's going nowhere to put it simply. Thanks to the review though I've made up a small checklist of sorts for later chapters.
EGS Character Insert Checklist
Must be less powerful than Grace, only slightly stronger than others, if at all.
Must have prior meeting with at least one character. (If male, cannot befriend Susan)
Cannot interfere with pivotal moments. (Goo defeat, Damien defeat, Ellen's creation)
Must not be written past midnight (My ideas get stupid right around then)
And that's it so far for the list. Hopefully I'll get the hang of these one-shots soon. But in the end, I'm not looking to add a new story arc to Dan's story, I'm hoping instead to go an alternate way with it instead.