From what the rules, and FAQ, say, plus some common sense:
Medium character, MWP only, two-handed: No penalty.
Medium character, MWP only, one-handed: -4 non-proficiency penalty.
Medium character, MWP only, Weapon Focus, two-handed: +1 bonus from weapon focus.
Medium character, MWP only, Weapon Focus, one-handed: -4 penalty, no bonus (character is not proficient with this usage of the weapon; Weapon Focus cannot apply)
Medium character, MWP only, Weapon Focus, Monkey Grip one-handed: -4 penalty, no bonus (character is not proficient with this usage of the weapon; Weapon Focus cannot apply; Monkey Grip, because Weapon Focus is a prereq, cannot apply)
Medium character, EWP, one-handed: As any other weapon.
Small character, MWP only, two-handed: -4 non-proficiency penalty.
Small character, MWP only, one-handed: Cannot use.
Small character, MWP only, Weapon Focus, two-handed: -4 non-proficiency penalty (Weapon Focus does not apply).
Small character, EWP, two-handed: No penalty.
Small character, EWP, WF, two-handed: +1 bonus.
Small character, EWP, one-handed: Cannot use.
Small character, EWP, WF, Monkey Grip, one-handed: -2 penalty for Monkey Grip (not sure if WF still applies; check Monkey Grip)
And an extrapolation:
Large character, MWP only, one-handed: No problem.
Large character, MWP only, Weapon Finesse: Cannot take Weapon Finesse: Weapon not considered light..
Large character, EWP, Weapon Finesse: No problem.
(Also see how this comes into play with two-weapon fighting)
(Not everything here is
clearly supported by the letter of the rules, but it all seems like a pretty common-sense extrapolation of the rules, which -- for purposes of proficiency -- treat the Bastard sword as if it were two different weapons. The Martial one is Large. The Exotic one is Medium.)