Okay, all of those are plausible interpretations except for the last one "per order, the same way you can choose between your Rifle or Pistol when declaring an Order or ARO". Because that's claiming that it doesn't do anything, and they meant to just use a comma.
I'm sorry, but how much detail does the rulebook really need to cover? Does it need to contain a dictionary of common English language practices? Does it need to contain a rules of customs for "when something looks really different from every other case, it really means there's something different going on, so it doesn't work like in all other cases"? There's a limit for which of these are reasonable to ask. I think it's reasonable to ask whether you make the choice on list creation or during deployment, but in all other cases the player must be able to realise that the unit's profile has something very specific going on when two skills are grouped up and separated by a / and it should not be hard for a player to realise what it means and that the decision should reasonably be made as soon as it becomes relevant. At some point, you have to realise that the question you're asking is fishing for creating uncertainty that you bloody well should know shouldn't be there in order to bend the rules to do stuff that they reasonably should not do.
Under traits for Heavy Multi, it lists Burst Mode as Shock Or AP. From this we can infer that the "/" on the profile means "OR". http://wiki.infinitythegame.com/en/Traits
Yeah, all I have is a vague memory where someone said that they were profile options and you had to pick one at list creation. But as you say that was 5 forums ago so I have no way of knowing if that was real, or even N3-related. The last example is intentionally obtuse, but serves to illustrate there's no reason it couldn't be that way. Without any rules to refer to, any of those four timing options are equally valid, even though they're significantly different in effect.
Yeah. ‘How to read stuff in unit entries’ is a bit of a blind spot for CB, which is why we keep having discussions about what + and / mean, across multiple forums and editions. My favourite is + being used for G: Servant and G: Synch, leading to a Scavenger that shanks an Auxilia being able to pick up a Combi Rifle with underslung Auxbot...
If you print a unit with the "/" you obtain two skills with a selection box to tick You have to choose one. Simply as that.