I can’t say I’ve tried this but the thought just came to me that generating such trades would be trivial to do monthly now.
In some countries (like Switzerland) you don't have any capital gain tax __unless_ you are a professional investor. What makes you a professional investor? One of the things that can elevate you to that status is the amount of trades you make.
So I am sure this is not viable for many people as buying an ETF counts like 1 trade, but investing the same money in the underlying assets count like 10s of trades.
Sure, if you want to print a 1000 page supplement and staple it to your taxes.
More seriously, I would still worry about order execution and transaction costs. You are likely to end up on the wrong side of the bid/ask spread when playing against the big boys.
If you're actually serious about this, you might as well start your own ETF. Or just buy this one I found after a quick Google: https://www.proshares.com/our-etfs/strategic/spxt Buying multiple sector-specific ETFs is another approach. I'm told that utilities are good to hold during a downturn.