Hmm for vows and obligations, you have two sorts, breakable, but not magically enforced ones, and magically enforced ones. The former now, I have a simple idea.
1) Select clause(s), clauses should generally put you in about as much trouble as benefit, in combination)
2) Select intensity(value from 1 to 5)
3) When performing an act directly promoting the clause, gain +intensity morale bonus to the roll
4) When performing an act contrary to the clause, gain -intensity morale penalty to any roll involved(this may reduce an automatically successful action to one you must roll for)
Optional rules:
5) When attempting to perform an act directly counter to the clause(or resist performing one directly promoting the clause), you must roll a Will save(DC 10+1/2 character level+2*Intensity), success means you do as you wish(with the morale penalty), failure mean you must follow the clause despite what good sense might tell you.
6) Subtract the intensity of conflicting obligations from each other when in conflict. Option 5 only applies to obligations with positive intensities, when conflicts exist.
You can use this to handle package deal things like codes of conduct or even religious laws. Option 5 may be a bit stricter than most players would prefer though.