It's kind of funny how everyone just assumes Sin Cara would be awesome in a ladder match or assumes he has tons of experience just because he's a luchador.
I find myself agreeing with you. There's this weird assumption based on what people have seen of "small but agile guy in ladder match" that all of them will be good at them. Sin Cara at this stage barely has anyone he can work with because his style's so different, and WWE can hardly put him in a program with Rey when he's supposed to be the "next" Rey.
While I find Sin Cara to be a really refreshing addition to the WWE roster, no way is he ready for this kind of match yet, based on his experience. He even had trouble being in the ring with Primo. PRIMO. Now I'm sure if Sin Cara and Primo had another match even as soon as in a month's time, while it would be utterly pointless in terms of Cara's direction, he would be better adjusted to it than he was a couple of weeks ago. Anyone know if Cara spent much/any time in FCW, just out of interest?
Now, I think (brace yourselves, here comes one of Paragon's many bizarre analogies) that to function well, matches, and the roster, in WWE style should be constructed like the class system in an RPG game. ("What?!")
You've got different styles of wrestler to create both balance and interest. So Sin Cara in his high-spot style, is the equivalent of a mage - uses cool-looking spells for massive damage! But ultimately lacks the durability and consistency of a simple-but-effective warrior, who while less flashy, can take a hit as well as dish out damage. Perhaps it'd be better if Cara, or for safety's sake, Morrison, worked this match with someone like Sheamus, more of a brawler/powerhouse style. So what does this freaky-ass metaphor mean?
Well, I think Sin Cara and JoMo should not work this match together, at least not now. As good as they both are in the ring with regards to their own styles, if anything goes wrong it could end up looking like something out of CZW (no offence to fans of CZW, I'm sure it does have its merits. Somewhere) Besides, their styles are quite similar in the way of using "high-risk" spots. I dislike the term "spot-monkey", because it's derogatory, and as I said, I believe you need different styles of wrestler in a company these days to keep it interesting. Which means that so-called "spot monkeys" are valid as a style of wrestler. But why not make it a four-way-dance, with some power or mat styles for variation? The ladder can be used for a lot more than jumping really high.
Sheamus, for example, is pretty good at the brawling/intense, measured power thing, but if everyone wrestled the way Sheamus did I know I'd be bored and I expect all of you would be too. Same way I'd be bored if everyone wrestled like Sin Cara. With a contrast of styles you have something much more interesting, in my view.
Another fairly long post so for
tl;dr, Sin Cara's style is not necessarily compatible with a ladder match at the moment just because he's a fast mover.
PS: I'd recommend paying attention to TWJC's post because he mentions storytelling which I forgot to bring up.