Converting them in small batches like 10K to 20K per day would take months to convert 1000ETH to BTC so the viable option to to pick the centralized exchange which obviously will have KYC but if you are from certain countries then you don't have to pay taxes for the crypto to crypto transactions because government consider it as assets so only time is we have to pay taxes at the time when we convert them into fiat.
Do you think I should really prefer this option?
What if the exchanger gets hacked and my data gets to hackers, I think I'd be great food for them and I'd probably get visitors very quickly.
What exactly do you think speaks against Cross Chain Swap or ETH-BTC Bridge?
The real problem will be liquidity in the cross chain Swap and decentralized protocols that uses blockchain so the conversion will be lot slower than you assume and it may even take days which I personally don't prefer.
On the other hand for someone with millions of dollar it is easy to proxy their real location by providing the identify from other geo location and let's talk reality they won't even use their real identity at all they can simply use someone and pay a hefty amount to them because there are lot of individuals are actually ready for such offers.