I've used the carbon/kevlar combination to fabricate RC sailboat hulls. The layup was into a female mold so the only cutting required was along the sheerline. The material will cut OK with shears after the epoxy/fabric layup has cured as long as it's not too thick. It does not tolerate sanding, so you only need to exercise care not to sand into the kevlar on the top of the coaming. No problem since you'll have glass over it. The edge of the coaming is another matter entirely. You might try laying up a layer of glass/carbon-kevlar/glass, remove it from the mold ~ cut it to size with sheers ~ place it back on the mold ~ add several more layers of glass ~ carefully shape and sand the additional glass, avoiding sanding into the kevlar.
Since an all glass or glass/carbon coaming is structurally appropriate (you don't want or need the flexibility or impact resistance of kevlar on a ridgid coaming) and you're looking for an interesting appearance, why not consider making the whole coaming out of glass using a transparent amber or yellow-brown tint in the epoxy? I'm entertaining that approach instead of carbon cloth on the Cape Ann Storm I'm building. In fact, I cut out the coaming opening tonight!