If anything, South Korean politicians are terrified by the perspective of North Korean regime falling.

For political reasons, reunification would be inevitable. It has been the stated goal of politicians for decades.

For economical reasons, reunification would be devastating. South Korea is not exactly poor, but the amount it would take to lift North Korea to a living standard which is not outrageously low (let alone comparable to the South) would be immense, and the living standards of South would plummet very significantly. This is a totally different kind of deal than reunification of Germany.

For cultural reasons, reunification would be a tough cookie. Nearly 70 years apart, in strict isolation, and under a constant inescapable brainwashing made North Korean culture drastically different from Southern Korean. Even the language evolved differently (and totalitarian regimes are keen to control and bend the everyday language to match their narrative). Now North and South are not separated brothers but more like distant cousins who grew separated by an ocean.

So South Korea will try to keep North Korea going as much as possible without losing face.

Source: a few lectures by experts in the question.