1. I would want the plausible lie of "it is an internal affair" to be the focus of our effort.
2. To that end, I would place operatives throughout Taiwan and have a coordinated attack on their infrastructure including crippling their power grid and communications.
3. The first strike force would attack in an unconventional manner, focusing on hindering troop deployments by blowing up bridges and roads.
4. Secondarily, I would attack the symbols of Taiwanese independence, their government buildings, their financial center, their police departments, and try to throw the populous into a panic.
All this could be done with patient planning and infiltrators. Most of the "invasion" could be done later as a stabilizing force, under the auspices of "getting Taiwan back on it's feet" and "restoring order." Europe and the UN would probably encourage the "peacekeeping."
Any coordinated attack requires some communication between those ordering the attack and those executing . The larger the attack and the larger the target set, the more communications required--one formula used by the US military for planning such attacks indicates that attacking a target set of N nodes (where N is greater than 1), using point-effect weapons (i.e., no nukes) would require N(N-1) coordination messages between the attacker's national command authority and the forces that would execute the attack. For even a modest-sized target like Taiwan, the number of target nodes is several hundred, which generates a requirement for many tens of thousands of messages. Facilitating this level of communication while preserving the covertness of the attack force is a nontrivial challenge.