Regarding the mosasaurus or liopleurodon, I think you need to first of all assume that they've greatly scaled-up whatever it is they're depicting. It's got a mouth the size of a great white shark (about 4 meters)? Neither a mosasaurus or liopleurodon comes close to that.
But hey, if you're getting into genetic engineering, I suppose you could make any dinosaur (or in this case, aquatic reptile) as large as you want. That how genetic engineering works, right?