It is quite clear that PLA naval and air assets are not sufficient by themselves to invade Taiwan. However, why must the Chinese restrict themselves to only conventional weapons? For example, here's one imagined scenario for a Chinese invasion, just from the top of my head.
Months (even years) prior to invasion:
PLA secret operatives and commandos are gradually smuggled into Taiwan, possibly via the "people-smuggling" rings that are currently active. They form independent cells in all major cities/towns, especially those close to major military installations or strategic locations. They independently organize to smuggle their equipment from China, possibly via black market smuggling. They assemble Electromagnetic (EMP) bombs in their hideouts, stock up on explosives and mines, then wait for the attack signal.
Weeks before invasion:
PLAN ships begin massing at invasion ports, perform wargames, missile tests, etc, just to keep the Taiwanese forces on high alert for weeks. I think its fair to say that its impossible for the PLAN to achieve tactical surprise even if they tried, so instead of trying to hide their activities, why not keep the Taiwanese on their toes with countless false alarms.
24 hours to go:
PLA signals its Taiwan-based operatives to get ready.
12 hours to go:
Chinese troops board transports/planes. But the first wave comprises of mostly older civilian ships that have been rigged to be remotely controlled, as decoys.
Finally, a few hours later:
Chinese operatives detonate all EMP bombs, disabling civilian & non-hardened electrical systems in major cities. Other operatives attempt to blow up bridges, mine roads, spread misinformation about Chinese landings, etc. Chaos ensues. Major freeways are clogged with stalled vehicles. While the army tries to restore order, Chinese commandos storm command centres, airfields, radar stations etc to cause as much disruption as possible. This is a similar tactic to that employed by the North Vietnamese during the Tet Offensive.
First PLAN wave crosses point of no return. Taiwanese forces finally decide this is the real thing, and scrambles fighters and ships to intercept. As soon as they engage the decoy ships, PLA launches massive missile barrage against Taiwanese installations and ships, followed by airstrikes by hundreds of planes.
At nightfall, transport planes arrive to deliver paratroops. Submarines attempt to land small raiding parties at all possible points to further confuse the defenders. When the main Chinese force lands, movement of Taiwanese troops to the actual beachheads are hindered by blown bridges, clogged roads and hit-and-run attacks by commandos.
The Chinese will use all possible means to inflict maximum disruption to the Taiwanese command and control, and hinder the movement of defending forces, to buy time for the invasion forces to secure a beachhead and push inland. I think unconventional forces will play a big part.
Alex
:lul