I worked in internal communications for many years and this involved a lot of work around change (both culturally and in response to enforced change). I believe that for positive change to happen within large organisations, the following elements are needed:
The leaders need to have time to truly understand the need for change and feel informed
You need people with the tools and skills to communicate that knowledge to others with passion and influence (identify those who do and those who don't)
Champions need to be identified at all (clinical and other) levels
One or two key objectives identified and prioritised to prevent it becoming an impossible task
A very clear comms plan focusing on just a few repeated key messages that reach the right people in the right way at the right time (face-to-face is so important where possible)
Regular check-ins with the champions and time allocated to this so that champions are not overwhelmed with an extra responsibility but instead feel inspired to act as an important driver in the change
Admin and project management input
I believe that a patient safety specialist could actually come from any of the above areas (clinical, project management, comms, senior manager etc).
No one individual will have the capacity or skill to do all of those points alone, effectively. What is important is that they are the type of person who is able to listen and learn from others and identify the team they need around them to give real change for safety a chance. Obviously this requires resource.... bullet points one and two may help inspire others to allocate resource.