You can play single player in disco 4.84 mod,it's way harder then vanilla.
I really don't remember do you need freelancer mod manager for that or not.
Also i don't know how will work with current 4.88.1.
New crossfire mod i god,i hear,considered to be freelancer 2 but i haven't played it yet.
I know it has more missions then vanilla added to storyline.
It requires FLMM but i don't know is it compatible with 4.88.1.