It's kinda like SWAT equiping out the traffic cop.
As soon as you add combat capabilities to a ship you start exponentially increasing crew requirements and sensor requirements. A 25mm can get buy with a dual use EOIR camera for targeting, and a Bosn with the right course.
A 57mm requires a fire control radar, air search radar and 57mm magazine and a combat management system. Otherwise you're completely wasting a capable gun designed for AAW to make loud noises and miss everything but stuff the 25mm can damage just as easily.
The crew needed increase by about 6 weapons eng techs for gun maint and misfire, radar maintenance, fire control maintenance, ammo custodian requirements. Then add 3 NESOPs (master and two S1s) to operate the gun.
The cost for all that stuff is now multiple millions of dollars. For what I would consider low capability enhancement for the mission sets required of AOPS.
So now you're walking back AOPS low crewing requirements, increasing cost for what gain?