HODL is common practice with many Bitcoiners but has anyone braved the risk of changing out BTC for a stablecoin to then change back into BTC when the price has significantly lowered to gain percentages?
Yes it is a common practice. We call it "trading". The basics are very simple, like you noticed, you need to buy low and sell high, then buy low again.
Binance is a good place to execute this idea because they also offer very high (10% to 20%, sometimes even higher) daily compounding interest on your USDT balance. Which means, you make money even when you are waiting in FIAT.
The biggest disadvantage is the risk you are taking by using a centralized exchange. If you don't mind it, then go ahead and make sum monneyy