>>27990661>>27993468Theres two ways I think you can get around it:
One is by essentially making up their own history. For example, making up the history and lore behind the Houshou Pirates. This might go awry but if you're going so far as to do a Servant sheet you're already one foot in.
Two is to use the rules established by TM to essentially limit how much you can do. Use skills they have already established, and use lore to limit power. etc.
I think a problem with fanmade Servant sheets is they get too bogged down on details and Fate (FGO even) always kept explanations and details in regards to Servant abilities on the minimum (outside of the story/main plot). Like, Saber's Invisible Air is three paragraphs, her Charmisa skill is three sentences.