My favorite system was in Dragon Age 2 where instead of paragon/renegade the protagonist had a personality determined by which of 3 dialogue possibilities you chose most often; Diplomatic, witty, and aggressive. It unlocked unique options for each personality and set the tone for their auto-dialogue. Maybe Mass Effect 4 should use this.
I enjoyed DA2's system a great deal, though at times it could definitely use some refinement. I was amused enough not to care too much about its issues though.
I liked the system as well, as it would let you be a total hard ass, but still do the "paragon" thing.
I felt that ME3 improved upon the R/P system by leaning more toward this, because Renegon can be little more than a personality change without actually taking the Renegade paths in the major plot points of the story. I certainly couldn't do it in ME2.