Concentric Vent Retrofit

Hi there. I have a gas hot water tank which vents through a 2" concentric vent on an outside wall. The vent is PVC and is connected to the existing hot water tank with ABS pipe. I'm changing the venting system to CPVC (System 636) in advance of a hot water tank swap-out and trying to figure out if I can re-use the existing wall vent.

My thoughts around options were:

1. Cut the ABS pipe near the vent, leaving a small stub of ABS with which I could attach a union using ABS / CPVC transition cement. This would make my life easy but might not address the code requirement in my jurisdiction (Alberta) for CPVC venting.
2. Try to find the "Y" piece (on the interior side) for a concentric vent and retrofit the actual vent piece. All I see for sale are complete vent kits, which suggest to me that cutting a vent kit apart may be easier said than done. I can only imagine that cutting and deburring may create more risk to my new boiler than is advisable.
3. Replace the vent altogether. The vent is only 11 years old, and I'm avoiding replacing it completely more out of the pain-in-the-neck factor than cost.

If anyone has any advice on how to proceed I'd appreciate it.