I'm sure they say in a video exactly what you said. 1 armour piece, 1 weapon. This is an incredibly good way to keep it balanced because nobody can ever become OP due to this limit and everyone will have their weaknesses still. Personally I think how they have done it is the best it can be done. In one of the video they show why this is the case, one of the exotics granted an ability bonus for the subclass of the character, any more of these and it would start to become ridiculous because you wouldn't be forced to make a choice as you are now. If they increase this limit people will just want more and more. Until people can wear complete sets and I definitely don't want that.