Random thoughts in regards to this...
I consider (and know) myself to be an absolute honest, and reputable seller here on ECT.
I'd think that payments should be handled by something other than PayPal, as anyone sending money (whether FnF or not) can easily charge-back the cash they've sent. This is a big part of the reason I quit using Middle-man services to begin with. It's great having someone else to verify accounts, and / or hold Kronos until payment is made to protect the buyer.. but, the sellers risks are still easily a factor as once everything is verified / kept on a 3rd party, the buyer still sends cash directly to the sellers cash account.
I dislike PA for various reasons, but, the one thing I did like (before I found ECT) is the middle-man disbursement method that they use. Hold / Verify someones payment for a few days until it "clears the system" then disburse the cash to the seller. I've thought about throwing in my chips to offer the middle-man services if able and / or allowed, but, if some shady buyer wants to pull the funds back to his account, now myself, the middle-man, is held responsible for that charge-back and not the seller. I've even done some reading into changing my PayPal into a business account to help prevent things from going astray. Although the more I read on this the answer I get from PayPal is still the same, charge-back via Banks is ultimately out of their hands.
I'm not sure if Venmo or some app that's similar offers a bit more protection for the seller, but now-a-days, even FnF isn't all that great.
The other issue I've thought about when it comes to MM services, that I've mentioned somewhere here before, is it seems most orders here are for Kronos. Which means a huge difference between ordering $9.50 per Krono, or $10.00. Purchase 10 of the $9.50 Krono and you're only saving about $5 compared to the guy whose charging $10 per, but that $5 makes the world of difference in which seller the buyer ultimately chooses to go for. For high-priced accounts, sure, an extra $5 - $10 per sale wouldn't make that much difference to a buyer, but it still offers nothing for the seller in terms of protection.
My solution is that I've thought about it before and can't come up with a clear-cut way to make it legitimately safer for both the buyer, and the seller.. unless there was a way to completely prevent charge-backs to the seller, the buyer still has ultimate protection or control over the sale.