To modify the Kingston class MCDV to be a better vessel for the task it does, here's a few suggestions.
1. Lengthen the ship by 20 feet. (better length/beam ratio = faster ship, better handling, also provides more space for additional crew)
2. Remove 40mm Bofors (most of which are dated from the 1940's, I saw them being re-furbed in the weapons shop in D-200) replace with modern 25mm Bushmaster (Smaller ammo, larger quantity able to be carried)
3. Add active stabilizers, provide better sea handling
4. Increase engine power available, or upgrade Z-drives, allowing greater speed (over 20 knots), allows greater flexibility and ability to be used for MIO Ops
5. Add IR/NV system to permit covert surveillance as part of MIO ops.
6. Add better Zodiac/RHIB system, again allowing better utility for MIO ops.
If the 20 ft section was added in midships, there could be more cabin space added, better stability, more speed, and a spot for RHIBs on each side.
The likelyhood of the ships being modified/improved in any significant way (such as adding 20 feet) is extremely unlikely, so the options most likely to provide improved capabilities for the MCDV's would be an increase in engine power to allow greater speeds, adding stabilizers, and adding an IR/NV system.
As you can see, I'm suggesting a lot of things that would allow the ships to be better used in MIO ops, (Maritime Interdiction Operations). Having a greater capability in doing this would make the ships that much more deployable, and because of their cheaper operating costs, they might be a better option to send in the case of a mostly MIO operation.
I do not think it would be a worthwhile option to consider increasing the armament on the MCDV's to the point of them being a major surface combattant, but adding a Stinger team, or Blowpipe might be a good idea, allowing for some local air defence in the case of a high risk area (especially if deployed overseas doing MIO in the Goo or somewhere.)
Just my thoughts, but adding a 20 foot section was proposed half-way through the build cycle on the ships (just as it was proposed to add 28 feet into the CPF's during building.)
NavyShooter