I created this package to allow for an easy drop-in for CKEditor. You can find it on Github here. If you use the package, you'll have to download CKEditor yourself. I'ts not included. Check the readme on Github for installation instructions. The class is well documented so you can have a look at it if you need more information.
Once the package is in your FuelPHP packages folder, creating an editor is a simple as this:
The most prominent change I made was made the functions static. This removes the need to re-declare any function(s) you wish to use in the bootstrap.php (or in this case, the core.php file).
After loading the package (either manually or through autoloading) you may now create an instance of CKEditor as such: