Amazing idea, and you seem to already have the follow-through sensibly worked out (that the bonuses don't count against the stat-cap, for example).
Third option definitely seems best to me. Have most of the 'basic' ones' articles visible from the start - things like Night Owl, Stormtrooper, Ice Cold Killer, whatever you get for being shot at/hit a lot - and keep some of the higher end, or niche/surprising ones hidden until achieved. So the player already knows they'll get a reward of sorts for one guy killing two or three targets in one turn, but it's left for them to discover if there's a special reward for killing say, six in one turn. Or so they can come across things like 'Traitor'/'Turncoat' (I forget the name, the one where you accidentally kill a teammate) on their own. Which raises its own questions as to whether that would grant a bonus or a malus...
Anyway, great addition, I'm getting so impatient waiting for 1.0 now! The whole lower caps, more bonuses thing sounds like a great antidote to the grindiness that was previously a bit much in the early campaign, so yeah. Can't wait to play it!