Don't be ridiculous. CGT coins and wire transfer would easily decrease customer base tenfolds, not to mention that cgtrader has no legal right nor resources to investigate customers financial history.
Payment reversal does hurt, of course, but it's really rare event and there's nothing you can do about it. I have about 2000 sales on cgtrader and from all those sales there were 2 or 3 payment reversals due to no cardholder authorization. That's a fraction of per cent. I lost less than $100 in lifetime sales due to this, but your proposed measures would surely cost me more than this each month! So no, thank you, but let's leave things as they are. You may be upset when you lose the sale because of chargeback, but if one day someone will steal your credit card, i'm sure you will be happy that such protection does exist.
BTW, i'm pretty sure that locking your files under the password is against the rules here and it's sure way to get refunds, customers complaints and negative reviews. Who knows, you might even get banned because of this. Just letting you know.