Probably not well. You'll be consistently betting against the market with very little reason to believe you're really adding information.

Also, cap weighting reduces your need to trade and thus your overhead and tax costs.

Interesting idea, even average would probably already work, it would give high performers some impact but not as much as now.

But it kinda misses what the S&P is in my pov. An index tracking how the value of those companies developed over the years measures by what you would have now if you would have invested in each of them