Quarterstaves should be classed as a special 'two ended weapon'. When used with two-weapon feats, it should work as two identical clubs, each in the main hand (same as crossbows). When used with two-handed feats, all glancing blows count as full blows and effects always proc. I'm not sure, but those might turn out to be the same, except under power attack. Cleaves should always do double damage, +1 [W] for each end.
Quarterstave melee should not be allowed on horseback.