Why do so many roll out stablecoins as THE option when there's no shortage of exchanges with real money? And some of have banking licences so that money is fully insured rather than being run out of a beach hut in the Bahamas.

It sounds like OP plans to 'time the market'. I doubt a newcomer would do a great job of that and nor would most people including me. You're better off riding it with a significant portion remaining in BTC. The market can give you a beating before you know it's happened.