Are your hens original line? I bet you could find someone to swap eggs with to get new stock.
Since the CCL was used to create the Isbar, I think you could add the CCL x to your breeding group as long as you kept it in "project" stage for at least a few generations to make sure nothing nefarious popped up. I would be much more hesitant about the Marans x as there are more genes there that could cause trouble down the line even if she doesn't express them. Size, feathered legs, and perhaps leg color just to mention a few. (I know both Marans and Isbars have dark legs, but I believe the Marans have a white/pink skin with the slate, while the Isbars have yellow with slate, or willow.)
thank you for the thoughts -- very similar to my own, which is why i'm only tentatively hatching ONE egg from the marans/isbar cross, to see what the result might look like.
and I have mixed feelings about genetic diversity vs. not being entirely excited about the look of the second line (yes, all of my birds are from the original line, although from different sources to me -- but they of course all originated from the same imports) -- genetic diversity IS important, but i'm enough of a biologist (which is to say, not much) to know of several instances of wild populations of animals that have gone through even more extreme genetic bottlenecks and are still doing okay -- hence my uncertainty about what to prioritize, diversity vs. characteristics of birds that i like or not?