If Emperor Hui isn't disabled, the Western Jin probably is maintained and China avoids a period where it falls apart.
But, there's also the fact that the country can't avoid some instability. There are still the various consort factions and rival imperial princes. There's also the fact that the preceding Wu and Wei empires where also quickly lost the moment a child/incompetent rule took the throne.
You wouldn't just need competence, you'd probably need some brilliance. Rebelling princes and nomadic invasions are still going to show up. I suggest that Emperor Hui function as a military general, for example, and that he should suppress the power of rival family members. Perhaps he should reduce their fiefs in size and power, and remove them from the most important parts of the Empire. In short, following in the ways of the Western Han.