The PAP is made up overwhelmingly of decommissioned PLA, so they can absolutely be used as additional light infantry. However, to use them as such would be a monumental waste of resources, and it would be hard to think of any realistic scenarios where this would be required.
That is not to say the PAP won’t feature in any Chinese military plans, indeed, it’s precisely because they are almost certainly prominently featured that just using them as light infantry would be such a waste.
The PAP are basically PLA veterans who have since spec’d into counter-terrorism, anti-insurgency, hostage rescue, urban combat specialists, with the added bonus of police work soft skills in dealing with agitated civilians in a non-American-jackboot manner.
After the PLA has won the war, the PAP will be the ones most likely to be tasked with the mopping up operations and for winning the peace. Since their train, equipment and expertise will make them the most suitable forces China has for the role outside to top tier special forces. The PAP should be able to handle the task with far less collateral damage and civilian casualties, and potentially even fewer casualties than if PLA regulars were tasked to complete the same mission.
