I suspect any nation with a coast guard would regard its coast guard as an reserve force in case of armed conflict. So these ships almost certainly have space, electrical power, wiring, and possibly also protection built in to swiftly receive substantial armament without any significant modifications to existing structures and interior partition.
IMO due to budgetary constraints, I suspect many coast guard cutters around the world are not built to strict military specs. For example, the MSA01 is a 5,400 ton cutter, and the construction cost has been cited at 350 million RMB ($55.7 million USD):
In previous discussions on this forum, the construction cost for 1,000 ton cutter in China is 100 million RMB (~$16 million USD) and 1,500 ton cutter at 120 million RMB (~$20 million USD).
While these coast guard cutters and OPV's can be up-gunned, most will never approach the capabilities of a real warship. However, the 056 corvette may be an exception. It's cheap enough to build as a OPV, but can be armed to serve the role of a light frigate.