I know they are almost never selected,
but there are options to start with higher or lower morality, putting you on the verge of light or dark side paragon. But whhile starting on the verge of light side paragon is fine, starting on the verge of darkside is counterproductive and painful... for the darksiders.
There are two architypes for a darkside main character. First there's the "deep end" murdurhobo "Kill the jedi children" sith, for whom Confict is a measure of his aliegence to the dark side. With the way the Morality mechanics are biased, there's no reason to start with -20 morality. He can start with extra stuff, then just kill 2 extra people and fall in the same amount of time it took the person who went for the "head start" option.
The other architype is the Grey Jedi, the well intentioned extremist, the person who fell but still holds a code. Sometimes a player even wants to run a redemption arc starting from evil. But again, they dont start play on the darkside- And that first session where you guarentee your fall may ruin the plan you had for your character, as you do acts your character is never planned to do again, just to slip down into Darkside territory.
I see two possible solutions. Either replace the -20 morality option with -30 morality (do NOT change the +20 morality option) to start you as a Dark Side Paragon, with -1 strain and a Dark Destiny Flip, Or simply say "-20 morality and are on the Dark Side for the purposes of the force die and powers." (wording may need cleaning up.)
Either solution removes the "First session" split personality and/or cash grab, and lets you start being a darksider from the start for RP reasons... which would be the entire reason for making that morality choice in the first place.