Well, you're going to have to go to some seriously heavy strings to do the job. At that point, you'll probably need to be filing bridge and nut slots. How high you set the action will depend on how heavy you go with the strings. Heavier strings will allow you to string it tighter and set the action lower, but that will put more pressure on the neck. Not sure how much more pressure or how much relief you can dial in, especially since you don't mention what kind of bass you're playing.
What I really want to know, though, is how you plan to effectively amplify notes in that range. Even on very solid basses, I find it hard to get a tight enough low B tone amplified. I can't imagine what it would take to effectively reproduce an F# below that and still sound like a bass guitar.
Personally, I would sooner tune or capo up to do what you want in the regular bass range. If you want to give the impression of that lower note, get a quality octave pedal and blend some in.