France is already quite a juggernaut in Europe. But if they tried to take Piémont and Catalonia as well, there will a immense coalition against it. Most it can do is to take/annex the french-speaking parts of Piémont (so savoy, Nice and the Val d'Aoste maybe). As for Catalonia? Well Spain is somewhat of an ally, why losing it for a piece of land which rather be independant than french anyway.
As for those you think France would have a better navy, that's not entirely true. Buiding ships is fine but you need sailors and France was quite limited on that. With Belgium, she can have 80000 sailors at most. Plus the french navy is pitiful in the 1740's, you need to build the 74 cannons model but it will take years if not decades to have a modern fleet again (the Royale back then was old, some ships were built during the War of 1700-1713) and to teach a new doctrine in naval schools (because french officers were not very competent -not a disaster either but still). Sure with the Low countries, she has the money to expand her army and navy but it would take time for the latter. I'm not even sure her navy would be ready for the SYW (if there is one).