I sincerely hope your suggestion never gets implemented because it would have catastrophic results for Chinese society. If universities looked exclusively at grades in one or two subjects for their entrance qualifications, it would disincentivize students from learning anything but the subject they want to later go into (which will most likely be that which makes the most money, so some subjects will become severely neglected by most students). This would be a disaster for society as it will create an entire generation which lacks the broad knowledge and understanding of the world to be responsible citizens later. You will have created a bunch of politically, historically and culturally illiterate STEM nerds who are going to make very poor and dangerous decisions about the future of their country. In the West, STEM students are among the most reactionary, misanthropic and poorly informed in their world views. The only groups with even higher tendency for reactionary views are economists and lawyers. A good system should foster a broad general education in its students. There is plenty of time to specialize later once the basis for being a well-rounded human being has been laid.

Also, that would not reduce the hyper-competitiveness of the system anyway, as you would still have many students competing for a limited number of spots at universities. They would just compete on more specialized knowledge. The only real solutions to decrease competition are either to create more capacity by building more universities, or to increase the value of non-university work qualifications such as vocational training, and then equalizing the pay levels between intellectual and manual labor.