Perhaps you could use your fiat to purchase a shipment of products, then create a retail website and sell those products accepting Bitcoin, and fiat, as payment?
That would be a solution, however that would mean setting up a business and putting in a lot of work. With a full time job and family, it wouldn't be doable for me.
Why can't you ever get fiat again? I've been under the radar with decentralized exchanges since I acquired my first satoshi. Whenever I want fiat, I'm just selling some of that via it; the financial institution you use doesn't know you're selling bitcoin.
That's actually one of the best solutions, but will it work for large amounts of bitcoin? Let's say I can accumulate large amounts of bitcoin by spreading out my buys for a long time in order to accumulate the amount I want (the offers usually are way below 1 bitcoin offers). However if I want to exit (sell the coins) some time in the future, when Bitcoin price has increase 10x or more, it becomes very cumbersome to do all these small sell offers on a decentralised exchange. Or how would you do this?
You can try looking for a trader in your area, someone willing to sell you bitcoin for cash in person. Just remember to be safe, meet in a public place, take someone with you so you're not alone and won't become an easy target.
This would bring the same challenge as above (buying through decentralised exchanges) with the added risk of actually meeting someone. And even if I could do it by getting bitcoin from people...someday I might need to get a large amount of fiat again in a practical way. Small sell offers on decentralised exchange over a long period of time will not really be a viable strategy. And selling it on a kyc exchange could have the exchange freeze my funds depending on the taintedness of the coins. And also I would tie my house address to a large sum of bitcoin.
In such case I would segregate my purchases. I will definitely buy it from decentralised exchanger where I don’t need to submit any KYC. Since it is big amount I will try to buy it from different accounts + different connections and different exchangers. I will make purchase on different days too.
This will reduce attention from any big amount altogether.
I have also had ideas like this i.e. to buy smaller amounts and send it to new addresses in my wallet in order to not draw attention to it. Then no one would be able to know that 1 person owns all these bitcoin. I guess that would be a quite ok privacy strategy. It will just take a while to accumulate, and maybe that's fine. But the day I need fiat, the bitcoin price might be 10x the amount or more. Then it will be quite hard to have a good exit (sell coins) strategy. The only thing you can hope for is that things have changed in a good way to facilitate this for large bitcoin holders who wants to exit in a private way
You are assuming that the criminals have access to the full database of centralized exchanges.
I just assume that if my house address is connected to my bitcoin purchase then bad people could get hold of this information either by being an employee (or knowing an employee) on the exchange or through the analysis firms which would also know. And the connection will probably be there forever. I don't like that footprint.