I'm not very well informed on the subject, but I think "Lend of Hodl-hodl" is the most appropriate option to do some of this, taking into account that you never lose custody of your BTC.

And on the other hand, taking into account that you must over-collateralize your loan, I think it's simply better to use your BTC to buy, or you make an exchange and that's it, in the end bitcoin is our "savings" and our "money" should be used both to save and to spend.