Is this technically feasible?
fake BTC's that can actually be moved to the culprit's account but totally useless?
They are called "test coins". You can pick testnet3, testnet4, signet, or regtest. The problem with testnets is that they are worth non-zero amounts, so they are no longer "fake". But yes, nothing stops you from using an altcoin, which would be based on Bitcoin, for example BCH, and pretend to believe, that "BCH is Bitcoin", and when you said "I have one Bitcoin", then you meant "1 BCH", instead of "1 BTC"
Test coins are useless because the relevant addresses differ from those associated with the mainnet.
This means you can't send your test coins to the address that scammers provide. Those involved in crypto-related crimes are often highly skilled, and the chances of tricking them are almost zero. If they catch on that you're trying to deceive them, things could end badly for you