My Civil war re enactor friend states that bayonets would only be used in an offensive/ defensive role if contact was anticipated.
As for 'wielding' muskets ala English Civil war 'reversed musket' style I feel that this would be a poor choice of tactic. Having played with a Springfield the other week I am firmly of the opinion that waving it around in this manner is a poor fighting choice. It leaves you open to attack yourself, never mind the thing causing mayhem on your own side as they duck. Try it in a confined space and it gets worse. Try it with a bayonet attached and you risk stabbing yourself.
Great for despatching fallen opponent by bashing their head in, but the balance of the weapon makes holding it at the correct end a better proposition.
Personally from a modelling point of view I would agree with the others. Include bayonets which can be removed with a knife if not required.