Louis "le Grand Dauphin" becoming King Louis XV could have good results. OTL, in the last years of his life, he secretly married his mistress but his father, Louis XIV, wasn't happy with this marriage. As a result, the "Grand Dauphin" retired to his castle in Meudon, which became the center of the opposition to his father's politics. Thus, maybe France could better beneficiate from enlightment under the rule of the "Grand Dauphin". This could butterfly the French Revolution.
The "Grand Dauphin" was also opposed to his father's decision to suppress the Edict of Nantes which guaranteed religious freedom to protestants. Not sure if he could, but maybe he would reinstute (or at least try) to bring back the Edict established by his great grandfather Henri IV.
The only problem I see is that the "Grand Dauphin" was far from intelligent. He said education had disgusted him from every intellectual efforts. This could prove disastrous.
It's the only problem with him as he was a rather kind, placid and discrete person. That could make him a popular ruler.
In overall, I think the Grand Dauphin could make a good king although he would probably stay in his father's shadow.
Then comes his eldest son, Louis, Duke of Burgundy, who would rule as Louis XVI in this scenario. The "Petit Dauphin" was surrounded by Aristocrats who wished for the return to a less absolutist monarchy with a little decentralisation as the Provinces would have had more power. Chances are high that the "Petit Dauphin" would apply these politics.
There is a problem however : from what I read, the "faction of Burgundy", the people who surrounded and supported the "Petit Dauphin" wanted only Aristocrats as councelors of the King : this means no Bourgeois. I'm not sure this would turn out very well for the economy, but I'm not experienced enough to judge.
Both of those reign would probably have an influence on OTL Louis XV, who would be the Louis XVII of this scenario. This, however, would recquire one thing : to have OTL Louis XV's eldest brother, Louis, Duke of Britanny (Born in 1707, died in 1712 OTL from smallpox), to still die as a child or to die young and without children.
The benefits on Louis XV would be great and he might turn out as a more competent king and a less sexualy obsessed person rather than a "Black Sun" like he was called in one of the documentaries realised on his life. With his grandfather and father assuming kingship before him, there would be no regency of the Duke of Orléans, nephew of Louis XIV and a very libertinate man.
What this could change also :
-OTL Louis XV may not marry Mary Leszczynska as this marriage was arranged by the Regent OTL. This thus butterflies his OTL children : thus no Louis the Dauphin (Louis XV's son) and no Louis XVI, Louis XVIII and Charles X.
-France might decide not to choose an alliance with Austria to an alliance with Prussia.