However, the 3-1 scoring in 1 vs 1 league due to c) made me think that it might be interesting to have a different score for "close matches".. something like "marginal victory" in BM.
Maybe make a 2 point victory if your coalition scores less than 30% more than the other coalitions?
So score 2 league points for a "close" game rather than have a bonus point for an overwhelming victory? If that's what you're suggesting, either sounds good to me.