Just out of interest, and because im making an expansion-like add on with the CK, i'd love to hear what everyone thinks would be suitable for a lvl 50+ challenge.

I'm quite interested in witnessing dragon's breath bypassing resistances - if anything positive came out of 1.2 it was experiencing how deadly dragons' breath should be as opposed to how wimpy it is when resistances work. I have no experiences with coding, so I'm not sure if it is viable to make resistances work for mages but not dragons? On the topic of dragons and drawing inspiration from AD&D, I would like more variety, like poison and storm dragons.

Darugr deathlords are supposed to be based off death knights. Rather than just shouts, they should be able to perform Incinerate, have high HP, regenerates HP, leech life and summon skeletons at will. If you take the time to craft a long back story and make just one death knight with the complexity of Lord Soth as a recurring antagonist, that's very much preferable to 50 generic draugr deathlords as bosses.

That's all I can think of at the moment. Is it possible to craft new monsters with the CK? If so, 7-headed Tiamat or beholders are on my wish list as well.

A bigger "Dragon Lord" that was more powerful and did some AOE spells on you, with a stronger main fire/frost/shock attack as well, and maybe 2 smaller dragons as well. Possibly a occasional kind of slowing effect as well just for that little extra challenge? just my idea from the top of the noodle

There is one dracolich in the game, but it is far too weak. If you can bump up its abilities like extreme frost breath, immunity to spells/frost, half damage from fire and shock while doing strong physical damage and ability to dual summon buffed atronaches, I think that's going to be a neat fight. Also, give more generic bandits the Bone Breaker ability, but keep it varied so that all sorts of weapons ignore 75% of AR.

what about landmass features? Questlines and so on

Landmass features? I'm not sure I understand your question. Are you asking about open world concepts from existing Skyrim landscapes? If so I think everyone is enamored with Blackmarsh, so make good use of those giant glowing mushrooms. The skeleton bridge at Sovngade deserves more visiblity too.

I like politics found in George R.R Martin's fantasy books, which means more power struggles amidst affairs between the Jarl's mistresses and conniving captains of the guard are welcome. Let the player have the choice of aiding the advlterous pair or play a dangerous game of exposing them to the Jarl, only to rewarded with a "promotion" of being relocated to the outer lands of Skyrim for broadcasting the Jarl as an impotent ruler who can't keep his woman by his side. The player can then take on the role of Count of Monte Cristo and attempt a stealth revenge plot of befriending the Jarl's allies, isolating them from him and usurp his throne.

I'd like to see a dungeon that involves a complete knowledge of Dragonshouts. Something that you need to have found most of the Words of Power, if not all of them, to go through.

We need more Humanoid Enemies, would love to fight some highly armored Marauder type NPC.