I have no doubt in this ability of PLA but it goes

beyond tactics of the battlefield. Geo/National strategies and Geo-politics must be considered. The new expenses of such bases and the ramafication of non-UN sanctioned move. Remember, it is NATO mostly in Afghan and UN played only a minor role. For PRC to go into Afghan using US, it must be UN sanctioned, PRC joins NATO, or go in alone. The latter two will be against PRC principles of non-alliance and using UN for "peaceful rise". Only way to go into Pak is to use SCO structure by making Pak a member. But we must consider India on this topic as well. Also, making Pak a member of SCO will eliminate Pak as a source of western techs and also squarely places SCO against US led NATO.
So, until the weighting of benefits vs liabilities are done and the right circumstances are created, no concrete actions will be taken by PRC in this area.