If they had that strength they would have done so already.
One can divide Republic of China forces into 3 groups with different motivation.
1. Patriots believing in the ideals of Sun Yat Sen
2. People who believe the status quo gives them and their families a good life and so is worth defending
3. Jap equivalent of neo nazis believing themselves under a secret mission to bring back Taiwan as a territory of Japan
I would believe that group 2 is by far the largest, and they're also ones which will initially offer most resistance to PLA, whereas group 1 will simply switch sides, because their interest is "a strong China" and since many years, they've been able to see how the Beijing government is far superior, especially in military strength.
The way Beijing can win over group 2 into switching side is by being lenient to rank and file fighters, but they also need demonstrate the ability of the mainland to offer far better living standards. Up until the 2010s, that was not always the case, but now, almost all tier 1 cities have superior conditions. Taiwan Chinese are already migrating to the mainland in search of better paid jobs, however, the people in this group needs to also be convinced that they will be equal citizens to mainland people in the tier 1 cities, just displaying better life quality is not enough if there is a fear that Taiwanese will be repressed.
Group 3 will fight to the death, but they're likely not too numerous in the actual fighting forces, only numerous among the civilian side of the leadership. The problem facing group 3 is that their ambition is inherently incompatible with either 1 or 2, so the moment they expose themselves too much, both 1 and 2 will turn on them.
