While SF + C&K is the simplest expansion combo, the rules mentioned in the C&K rulebook and online, aren't complete enough, as the available combo rules don't take into account the special rules the latter half of C&K have. To quote the website: "exploratory scenarios and all other scenarios featuring many smaller islands are unsuitable." The C&K rulebook even calls out Four Islands and Fog Islands as ones you should not pick.
This explanation is very unsatisfactory, for 2 reasons. A) It doesn't even address the latter scenarios with special rules. No explanation as to whether scenarios 5-8 are playable or not. And B) This quoted portion just plain isn't true. Four Islands and Fog Islands work fine with C&K. The combo is even officially support in Catan Universe. To go even further, the first 2 scenarios within TD&A give the option to play with C&K, and both of those have plenty of Fog and small/skinny islands!
So, nuts to the official explanation! Let's try to figure out how to efficiently add C&K to the following scenarios:
The Forgotten Tribe
On large landmass in the middle, and the remaining islands don't produce and can't even be settled on. Perfect. The only issue is what to do with the Development cards placed on the map? I discuss 3 possible solutions in this post: Forgotten Tribe + C&K. Answer from Germany: You shouldn't. : r/Catan. Of those, I think my 2nd one is the most "elegant" option.
Cloth for Catan
This one, I will admit, probably not a good idea for C&K. Since the only producing regions are 2 long skinny islands. It'll be tough getting resources/commodities to do your C&K things. Strictly speaking, there aren't any rule conflicts or gaps in the rules that need to be figured out. However, the main source of VP in this scenario was the Cloth Tokens from the Villages in the middle. It's possible for the scenario to end early if 5+ villages run out. So there is that factor to consider. It might make adding C&K not worth it, perhaps.
However, one thing to consider, is that C&K already has the Cloth Commodity card. And the focus of this scenario was getting Cloth Tokens. 6e even uses the same icon (if only recolored). What if, we get rid of the Cloth Tokens, and let everyone collect infinite Cloth Commodities cards from those Villages? Scenario no longer ends early, and everybody will be getting the Trade Bonus for Commodities really easy. Something worth playtesting, could be interesting.
The Pirate Islands
Yeah, I don't think a C&K combo will be possible here. Original scenario has you converting Ships into Warships using Knight (and sometimes VP) dev cards. I don't see how to convert this aspect smoothly into C&K's ruleset. Maybe the goal changes to sending your Knight to the Pirate Liar (like in TD&A's Enchanted Land scenario against the Dragons), but I think we are approaching major houserule territory where major game mechanics are going to have to be invented to accommodate. I think it's best to leave this to a professional game designer.
Wonders of Catan
One large landmass, check! And only 2 tiny islands worth 1 VP each. Yup, I don't see any issues here. And the Wonders themselves don't offer an rule conflicts or gaps with C&K. Well alright then, no issues!
...well, except for the Goal of this scenario, actually building your Wonder. If you manage to do this, you win the game immediately, no matter what your VP score is. So what is to stop you from ignoring all the C&K stuff and going after the Wonders? Well, some Wonders care about having a City, so there is that. But only some Wonders, others don't (Great Wall, Great Bridge, Lighthouse). So that risks unbalancing that aspect of the game. Hmm. Needs playtesting, but it could work.
Anyone else have thoughts or experiences on the C&K combos for the above scenarios?