Hytham is an NPC that serves no purpose once the Order of Ancients have all been killed. In order to make him (and the Hidden Ones) more relevant to the overall game, he should offer repeatable side activities in the form of "Blackbox Assassination Contracts". These contracts should be to hunt down the remnants of the Order of Ancients Hytham mentions after you kill them all. They could function similarity to the Blackbox Assassinations seen in the Siege of Paris DLC, giving the player multiple methods of killing a target.

Since these missions are repeatable, naturally they would become repetitive as there are only so many locations for Blackbox Assassinations. However, I believe having the option to repeat Blackbox missions using a variety of tactics would make them more enjoyable, along with having rewards in the form of skill points, materials, and gear/weapons with Hidden Ones aesthetic to them.

Furthermore, every map in the game - including DLC areas - should have a Hidden One NPC to give you similar contracts. (Excluding mythical areas for obvious reasons). The rewards would be the same in every map, however each area should have certain gear/weapons unique to their location. This would give other maps in the game more replay value, and add to the overall lore of Assassin's Creed. (*Spoiler: Such as the Hidden One in Siege of Paris)

Personally, I found that the Blackbox Assassinations were the highlight of the Siege of Paris DLC. They reminded me of old school Assassin's Creed, and I feel many fans would agree. However, I was disappointed I couldn't repeat them once completed. These contracts would allow players to enjoy them endlessly and give them the Assassin related content so many have been asking for.

What am I missing about Vinland? It’s a beautiful zone. It looks like a lot of work went in to constructing it. But outside of being a place you need to go to in order to kill a certain mob, what is the point of spending any time there except to kill him? I managed to kill him when I was only mid-level with nothing but a club and no armor. Bing bang, and I was out of there. I left and didn’t return until just a few days ago. I had completed Ireland and really had nothing much else to do, so I decided to go back to Vineland and see what was there.
 
And what was there? Not much. I could gather wealth and complete mysteries, and that was about it. There certainly were no other quests. I ran around and got all carbon ingots. I managed to get enough leather and iron to buy the armor body and helmet. But what was the point? It’s not as if I needed that stuff to complete quests, and there didn’t seem to be any point in spending any more time there harvesting iron so that I could get the remainder of the armor set. Why get it if you can’t take it back to England? Granted, it’s not very powerful, but it is kind of cool looking, and now that I’m so OP I wouldn’t mind running around in gear that offered not much except good looks.
 
And so it looks like we have a beautifully designed zone that really has no purpose. I mean, why not just put that mini-boss somewhere in Norway and killing him there? Am I missing something?