A suggestion for China to defeat Taiwan.

Rather than invading Taiwan.
The Chinese could organise a military coup against Taiwan.
Although this may seems unlikely but never impossible.
The CIA has funded rebellions over the world, China could sent in spies to inflitrate Taiwan's government.
There are some Pro-Chinese groups in Taiwan. Especially older people, ex-KMT troops from mainland China. Some of divided by the rest of their families after the war, wants to return home.
The Chinese spies could use "stop Taiwanese independece" as a reason, to lead a military coup against the government. After it succeed, may establish a pro-chinese government(similar to the situation in chechenya). This will act as a provisional government until the Island eventually returns to mainland China.

There are plenty of Chinese secret operatives living in Taiwan and conducting espionage and feeding back information to the central government concerning separtist and pro-independence activities.

There are confirmed cases by Chinese spy defectors that there are a crazy network of Chinese spies operating overseas in Western Europe, United States, Canada, Taiwan, etc.. gathering intelligence and weapons information for the CCP government. Most of these information goes back to the PLA military. Even there is operatives in Hong Kong gathering intelligence on the Falun Gong movement there.

So I do believe China has operatives trying to instigate a coup. How difficult is to gain the trust and commitment of the ROC Army generals to mobolize their forces and subordinates against the central government when the status quo of Taiwan is prosperous? Under current circumstances, I doubt the military leaders of the ROC Army would ever consider backstabbing its own government when there is not really any justification or valid reason to do so.

Here is a better way to invade Taiwan:

Create a Blue water navy capable of protecting China's sea lanes of communications against the American navy.

America's 14 naval strike groups can cut off oil supplies to China in event of invasion via the Straits of Mellaca in South East Asia, were 80% of China's oil supply from the Middle East goes through. The extent of the Chinese navy to protect their oil ship lanes will be crucial to the success of a war against Taiwan.

If I am not mistaken, China's navy does not currently have blue water naval capability but does have the range to project naval sea power down into the South China Sea where the Spratly islands are.

I don't see any nation including China to be able to catch up with the status of the American navy anytime in the next 50 years. China must modernize to fight a limited protracted with with a high tech enemy. It must paralyze the American navy for the split second time frame to achieve mission accomplishment because China cannot risk sustaining a prolong protracted with Taiwan's navy or America's navy because it simply cannot win against America's naval might.