Unfortunately none of these suggestions are fool proof, and will fully protect you from chargebacks. And for some (especially new sellers), a 5% loss rate (referring to LeagueSmurfs 95% win rate), can be catastrophic for a business (PlayerAuctions for example would have died a long time ago with loss rates that high). So it really depends on your profit margins, and if you can afford those kinds of losses to begin with.
One additional factor you will need to take into consideration if you are starting your own RMT business, is PayPal's dim view on virtual goods trading. Because virtual currencies have come under scrutiny and have issues with federal compliance laws, unless you keep very good paperwork/documentation, it is possible to get *YOUR* PayPal account locked or limited.
About 4 years ago, I approached a large seller about potentially starting a partnership with us by opening a store on PA. He was interested of course seeing it as an additional channel to acquire users, BUT he wasn't in any rush to get it done...until...
... he had his PayPal frozen... with $50,000 inside of it. Unable to supply PayPal with the necessary documentation they requested for their KYC compliance policies, he basically had to shut down his business the next day, and transfer his whole store into a PA storefront, thus beginning his most profitable venture to date. He wasn't able to retrieve his $50k from PayPal unfortunately.
Unless you are very brave and willing to risk a situation wherein you have a large amount of funds no longer accessible, or just having your own PayPal accounts limited, it would be unadvisable to do direct trading with other users.
You *CAN* prevent chargebacks and risk to your personal PayPal by opening a store on PA, but if you 100% prefer to do it alone, there is ONE way you can prevent chargebacks, but it is so inconvenient that it just doesn't work for our type of business. A) Buyers wouldn't opt for that type of order confirmation and B) Sellers would have to invest too much time to make it work.
PayPal is an aggregator, NOT A BANK. In order to win 100% of your chargebacks, you'd need to present the same type of evidence that would convince a bank, because if the scammer bypasses PayPal entirely and initiates the chargeback at their bank, then PAYPAL has to defend the merchant TO THE ISSUING BANK, which is not something they are usually willing to do unless they have foolproof evidence.