Is there an option? Yes
Will it be easy to maintain and guarantee to be unproblematic:
Probably no.
-> especially as you're now asking for 7.4.0,
which you should keep up-to-date. Remember: If there's any security
related patch or update, it likely won't be reapplied to 7.4.0, but to
7.4.x (whatever the latest x is), and you should be able to carry your
customization forward without much work.
What's the version that you want to upgrade to? (If I remember
correctly, there was a license change in some ckeditor major version
that prevents updating to a version that's available under the new
license - but I might be wrong on that)
