It IS possible to implement ISO 9001 within one department, and gradually expand the system to others. In an earlier position, I was involved in successful implementation of ISO 9001 in a single department of a major company. The department was one of the smallest in the maintenance division of a major international airline. In the 10 years since, the number of departments covered has expanded so that nearly 1/3 of the maintenance operation is under ISO 9001. This is partly because of customer requirements and partly because some managers have seen the value in it. (The value comes from increased efficiency, allowing the throughput to nearly double while maintaining the same staffing level.)
I do have a couple of cautions.
First, you must explicitly define the scope of the ISO 9001 system. Since you mentioned silos, focus only on what happens inside a silo as the system. Everything else is inputs or support services. Later you can add additional silos and expand the scope of the ISO 9001 system. If the quality manual is well designed, the quality management system itself does not necessarily have to change. (Remember that the details of the work and how to do it belong in the QM; they are the realm of polices and procedures that may be referenced in the QM.)
Second, you have to be sure to define the rest of the company as a supplier and as a customer. For the rest of the company as a supplier, you must treat them as any other supplier – including being listed on an approved supplier list.
While implementing the system for the entire company may be preferred, doing it incrementally is also possible.
Resistance to change, whatever the stated seasons, will always be there. It is one of the things that top management has to address, preferably by example.
GCP