If you're going to stock pick, this is the worst way to do it IMO.
1) Nobody can know enough about 50+ companies to make an intelligent decision.
2) The bulk of SP500 returns come from a relatively small amount of companies on any given year. Often, they are surprising. Miss a few of these and you'll underperform.
3) Attempting to figure out when to sell this volume of companies would be... exhausting. Hold forever doesn't really work with individual companies.
If you're intent on investing outside of an index, do it in a very focused way.* Focus on industries you know well and research the individual businesses thoroughly. When you find the right one, make a significant bet.
*Not necessarily recommending this, but the odds of success are much higher than "make your own index" IMO.