..I'm not sure you read the same fic I did. While you're apparently much more familiar with the RPG systems involved than I am, I am at bare minimum not sure where you're getting the "using a character build that someone else designed" thing from; the way I read it, he was specifically designing a build on-the-fly based on his own familiarity with the various D&D systems which seemed to be being used and on the exigencies of the situations he found himself in.
If nothing else, the reference to not having the spreadsheet he was used to using to keep track of skills and feats and levels per class and so forth would seem to indicate that he was at least used to designing these builds himself before all this happened...
And to keep this vaguely (vaguely) on topic, there's a sequel to the same fic also available on the author's page, done as a HP crossover. Unfortunately, it's incomplete, and the author has stated that it's unlikely to see an update ever again.
If nothing else, the reference to not having the spreadsheet he was used to using to keep track of skills and feats and levels per class and so forth would seem to indicate that he was at least used to designing these builds himself before all this happened...
And to keep this vaguely (vaguely) on topic, there's a sequel to the same fic also available on the author's page, done as a HP crossover. Unfortunately, it's incomplete, and the author has stated that it's unlikely to see an update ever again.