On topic -
I'd love more skill trees, but I think Beth may have somewhat painted themselves into a corner here.
In previous titles, skills were simply listed on a chart. If they
had wanted to add a skill, they could have just tossed another line at the bottom of the chart.
In Skyrim, we have the constellation thing. Each skill fits under one of 3 constellations, with each constellation 'governing' 6 skills.
So, would the lycanthropy skill tree be a Mage skill, a Warrior skill, or a Thief skill? No matter what they decide, now we have one constellation governing 7 skills.
I guess you could put Lycanthropy in the Warrior constellation. If vampirism also gets a skill tree, perhaps that would go under the Mage. That leaves the Thief without a 7th skill, to keep it 'balanced'. What should be added? (My vote is Acrobatics

)
The other way to go would be to just add the new tree/s and not attach them to any constellations.
Either of these solutions results in a potentially awkward looking skill menu. Not that I care how the damn thing looks, but Bethesda does - they apparently value the appearance of the menu even over its functionality. (insert UI rant here)
And a lycanthropy tree would really almost demand that we have more than
one single way of contracting lycanthropy. A perk tree devoted to members of one single faction? No other skill is like that.
Don't get me wrong, I would
love more skills and perk trees. But there are some obstacles to making them fit in.
Now, with crossbows, I can see those being given their own branch of the Archery tree. Of course, 'Overdraw' doesn't sound right for crossbows. But most of the other perks could apply, I think.