A practical replacement for the Archer-class patrol boats

What should replace the Archer-class patrol vessels in the Coastal Forces Squadron, and how should it be armed?

Choose a vessel of similar size with heavy machine guns and provision for a 20 mm mount or equivalent weapon.

The Archer class consists of very small fibreglass patrol vessels normally operated by four or five people. Their association with university naval units helps define the scale of the replacement being proposed. A similar-sized vessel is preferred. It should be able to carry heavy machine guns and have provision for a 20 mm mount or a weapon of equivalent calibre.