Louis XVIII's influence on the Revolution was insignificant. He was in opposition to his brother till 1789 (he was one of the proponents to the doubling of the number of Third Estate delegates), but since the summer of 1789, he was an unremarkable part of the "Court party".
On the other hand, Louis was fare more realist than his brother Charles, and able to see the necessary middle way in 1814/1815. One might assume a son of his could have followed the same path, thus avoiding the 1830 Revolution, but even Louis-Philippe, a more liberal-leaning ruler than Louis XVIII ever was, finally ended up with a Revolution. Except if Louis XIX showed exceptional qualities and muted the regime to a true constitutional monarchy, the Bourbon rule is doomed.
On the other hand, Louis was fare more realist than his brother Charles, and able to see the necessary middle way in 1814/1815. One might assume a son of his could have followed the same path, thus avoiding the 1830 Revolution, but even Louis-Philippe, a more liberal-leaning ruler than Louis XVIII ever was, finally ended up with a Revolution. Except if Louis XIX showed exceptional qualities and muted the regime to a true constitutional monarchy, the Bourbon rule is doomed.