In this case, any Instant exchange can be suitable for him. Blockchain analysis companies won't investigate unless they are hired by someone to trace anyone and in this case, OP have no concerns about it.
I don't think this is a good idea. While it is unlikely that a company will investigate him out of nowhere, the chance of his data being sold or accessed by malicious parties still exists. Not to mention the risk of using instant exchange for his fund is quite high (KYC, terrible rate, etc). If I learn anything from Chipmixer or how mixing companies store their customer's data while they claim the opposite, it is unwise to assume nothing can go wrong at all.