So technically, Taiwan considers itself part of China, in an abstract sense.
More info please, this isn't what I know of Taiwan.
Aside from escalation of tensions, pissing off PRC would likely worsen economic relations, which I think would be more damaging to Taiwan than to China (according to Wikipedia, China is Taiwan's largest import/export partner).
Absent the political/economic ramifications, I believe only a very small percentage of Taiwan's population would mind if Taiwan renounced these claims. Even "pro-reunification" KMT has stepped a bit back from its reunification stance, e.g. setting conditions like "democracy, economic development to a level near that of Taiwan, and equitable wealth distribution" for China before reunification can occur (https://en.wikipedia.org/wiki/Taiwan).
So, for many, the only reason to support an "eventual reunification" stance is it'd strengthen the economy, i.e., they don't mind China playing its word games if it means peace and Taiwan prospering.
This doesn't mean "pro-independence" pan-green party ignores the economic effects. They argue for developing economic relations with other countries, to reduce economic dependence on China, and thus make independence more practical.
KMT values economy over opposing "one China". I would say DPP values eventual independence more, but they still recognize the economic ramifications and thus seek to develop economic relations with other countries to reduce reliance on China (but how successful this has been is debated).
Anyway even DPP says they support "one China" to some degree, they're just more willing than KMT to risk supporting it to a lesser degree.
I doubt very many Taiwanese people actually care about leading China or believe that ROC will ever become the de facto government over all of China.
The only reason that Taiwan gives the perception that it supports re-unification / "one China" (part of which includes maintaining its claims over mainland China) is to maintain good political and economic relations with China. Because opposing re-unification would piss off China.