[@Abefroeman] It's an interesting concept certainly, and very well thought out. There are two issues with the sheet however. 

1) There's not much information on Truth but we can surmise it's the Rogare family's ancestral sword. I don't think it's likely for the son of a thirdborn to inherit such a prestigious weapon. The firstborn son would likely want to hold onto it to keep it in the family, so Maelys' chances of inheriting it wouldn't be good. 

2) In the background info, it's explained that the man who claimed to be Aegon Targaryen in the main series was actually Aegon Blackfyre, a fact unknown even to him, as per the popular fan theory on Aegon's true lineage. Aegon renounced his claim but became a dragon-rider and settled in Dorne and married into House Martell. So if you want, you could have Maelys be one of Aegon's children. His history would be altered somewhat, but he could still have earned his spurs in the Stepstones and have the same motivation of redeeming his ancestors. Conceivably, Aegon could have given Maelys Dark Sister. Aegon was legitimized by Jon, and Dark Sister is given to worthy Targaryen warriors rather than on strict inheritance, based on the history of its ownership. An alternate idea is that Maelys is the descendant of Aerion Blightflame, himself a very infamous person and definitely a family lineage that would need redemption. 

Other than that, the sheet is pretty exemplary and he seems like an interesting character.