The thing that most attracts me to historical fiction is taking the factual record as far as it is known using that as scaffolding and then letting imagination build the structure that fills in those things we can never find out for sure.
May He who is the Brahman of the Hindus the Ahura-Mazda of the Zoroastrians the Buddha of the Buddhists the Jehovah of the Jews the Father in Heaven of the Christians give strength to you to carry out your noble idea.