So if someone does this, would you recommend selling the btc from the altcoin sale immediately for usdt immediately or not? Then when you are ready to buy back the altcoin at a lower price, you buy btc immediately with usdt... then buy the altcoin immediately with usdt.
You literally asked this same question in another thread. Why do you expect a different answer this time? If you're so intent on selling your altcoins and holding USDT then just do it. Why do you keep asking people whether that's the right thing to do? Nobody is here to trade for you. USDT is for hedging dollar value. Nobody can tell you how do hedge your money, especially when it seems like you don't like to listen to sensible advice.
Again, I'm trying to impart my experience here. Your stated strategy will probably end up losing lots of coins repeatedly because of how thin altcoin markets are (and also how thin BTC/USDT is). You're likely to sell after the panic has ensued and you'll never get your altcoin entries back. Panic selling into two thin markets after the dip is already happening? Good luck not losing money. It's a horrible strategy. If you don't know how to baghold altcoins and you're constantly concerned about hedging their USD value, you will lose
lots of money trading them.
Thus you dont have to think about the btc price fluctuations.
Anyone who trades altcoins and thinks they don't need to consider BTC price fluctuations is a losing trader. It's that simple.