In the anime series "Ouran High School Host Club" Kyoya Ootori stops the Tonnerre family's hostile take over of Ootori Medical, but nothing is said about the Suoh family's company.
Couldn't Eclair's family, out of spite for Tamaki ending the engagement, try the very same thing with the Suoh company?
It was a concern for Tamaki's father and grandmother. I believe it was the whole reason the grandmother set up the meeting between Eclair and Tamaki. So that they'd get engaged and the Suoh family would still have a hand in their business.