If I were you and you wanted to create a kotor 3 storyline based on the revan novel.
To draw it out a bit more, I would have Lord Scourge as the main character of the story
specifically because Revan and the Exile are already fleshed out characters that have extensive
backstories. By the time they go to reach the empire. They are already overpowered and it would
make no sense to retrain them. Lord Scourge or Lady Scourge if you give the option that character being
female allows for some room to build a story. You can start with the training on some sith conquerered world
that has an academy and really gives some insight into what actually happened to the True Sith so their society
is fleshed out more and you can explore a more morally ambigious character of a Sith pureblooded male or female
who rises to the rank of Sith Lord in a society that conquers, prizes the strong over the weak and yet still maintains some
order so that the empire can grow and grow in secret. You finish your trials as a Sith acolyte before becoming a Sith Apprentice
to some unknown Sith Lord and you are sent on some conquesting missions that earn you the rank of a Sith Lord which in some way
should involve you killing your Sith Master which is a requirement for any Sith Lord really. That should put you on the path
where the book starts with Nyriss and the assassination attempt made on her life which leads you to meet Revan and the Exile.
My advice in order to keep canon and non canon people happy is to just introduce them as The Revanchist if lightside or Darth Revan
if you make Revan darkside in your choosing of gender and story ending. Same with the Exile. In this way you leave some leeway for
people who want to create a non-canon world. The traditional lightside ending should end like the novel. But the darkside endings
could be something that ends in a free-for-all between Lord Vitate, Darth Revan, The Exile and Lord/Lady Scourge with multiple
endings like Lord Scourge reforming the Sith Empire from knowledge he gained during the journey or Darth Revan becoming the Emperor or
the Exile becoming a new Darth Nihilus since the Exile and Darth Nihilus are both wounds in the force. Regardless I believe your best bet
for a really good gameplay experience that is based on the Revan novel is to start with a character like Lord Scourge because
either way the novel ends in darkness. Kotor 1 is a story that is relatively Grey because Revan traveled both roads only to come to the middle.
The Exile is pretty much a Jedi in all respects for the KOTOR 2 storyline in my opinion. So go really Dark in your story from the beginning.
It would probably be best from how I can see it.