No, you can’t remove the cancel permission while keeping add and amend permissions in a worker role.
The cancel system functions CP_CANCELLATIONS relate to the care package screens via the Person Summary screens, so you could theoretically cancel a care package this way and not via the workstep, or vice versa. However, the system is currently working as intended.
If you still require this, it would need to be a product enhancement or new feature request, which can be done through an AHA request.