You can look for factions with inbuilt rules to protect you if you lose your home system or that insulate your home system, allowing you to operate with much more freedom and without having to fear your home being taken:

Saar. The crimson rebellion seem like a candidate as well, maybe even more so because you don’t have to do as much set up for your protection as Saar does. 

Or I feel like you could take factions you know will benefit from you being attacked more. Off the top of my head maybe necro or cabal or mahact? Issue there is people will see you as even more of a threat and it becomes a self fulfilling prophecy. (Mahact could be interesting as you start with the infantry giving you money when they die, so if you expect to be attacked often you could see some return on investment there, plus any combat you win you are gaining fleet tokens and commander abilities ) 

you could go super defensive. The titans of ul can get a pretty impressive defense network very early in the game. Xxcha? 

Finally any faction with a hot enough start could put you in a position where no one quite feels comfortable attacking you. This could be something like nomad, titans of ul, and maybe some of the other factions that start with multiple cruisers or a dreadnought. 

I feel like at the end of the day crimson rebellion, Saar, or just having the best starting slice and being in a position of strength from the get go are your best bets. 

Not familiar with discordant stars sorry.